Since the successful launch of the Suomi NPP on October 28, 2011, the VIIRS instrument has performed well in general. This paper provides an overview of the evolution of the VIIRS instrument performance, major events experienced in the nearly three years since launch, and the ground processing system changes to account for various effects and discrepancies. The mirror degradation in the near-infrared bands due to prelaunch mirror contamination has been gradually leveling off, although the degradation in the solar diffuser continues. In the ground processing, many changes have been implemented in the operational code. This includes the stray-light correction for the Day/Night band, the automatic calibration for the reflective solar band, and corrections for several errors in the code, and resolving various discrepancies in the calibration equations and coefficients. The scientific community is generally satisfied with the quality of the VIIRS SDR data. However, there are remaining issues to be resolved through further research and development. These issues include meeting the more stringent requirement and desire for ocean color applications, better understanding of the polarization effects especially off-nadir, understanding and resolving inconsistencies between solar and lunar calibration. The Suomi NPP VIIRS SDR has been used for generating a variety of products with great success by worldwide users. Together with the follow-on instruments J1 and J2, VIIRS will be the primary data source for moderate resolution satellite observations in the next decades.

The European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) are cooperating to develop the EarthCARE satellite mission with the fundamental objective of improving the understanding of the processes involving clouds, aerosols and radiation in the Earth’s atmosphere. The payload consists of two active and two passive instruments: an ATmospheric LIDar (ATLID), a Cloud Profiling Radar (CPR), a Multi-Spectral Imager (MSI) and a Broad-Band Radiometer (BBR). The four instruments' data are processed individually and in a synergetic manner to produce a large range of products, which include vertical profiles of aerosols, liquid water and ice, observations of cloud distribution and vertical motion within clouds, and will allow the retrieval of profiles of atmospheric radiative heating and cooling. The presentation will cover the configuration of the satellite with its four instruments, the mission implementation approach, an overview of the ground segment and the overall mission development status. The four instruments performance, based upon currently available analyses and test results will also be briefly addressed with a focus on the ESA instruments.

Total Solar Irradiance (TSI) has been recorded daily by Total Solar Irradiance Monitors (TSIM) with overlapping measurements on FY-3 (Feng Yun-3) series satellites since 2008. Instrument descriptions, operation in space and flight performance of three TSIMs are presented in this paper. TSI is measured by electrical substitution radiometers integrated in TSIM, with traceability to SI. TSIM/FY-3A and TSIM/FY-3B share nearly the same design. Since TSIM/FY-3A and TSIM/FY-3B have no pointing system, the Sun is only observed when the Sunlight sweeps TSIM’s field-of-view and TSI measurements are influenced inevitably by solar pointing errors. TSIM/FY-3C, a radiometer package was constructed with a pointing system for solar tracking in order to achieve accurate solar pointing. TSIM/FY-3C was sent into orbit in September 2013 onboard FY-3C satellite. Daily TSI measurements have been performed by TSIM/FY-3C with autonomous accurate solar tracking for 1 year. TSIM/FY-3C is in a good instrument health according to its on-orbit data.

Intercalibration against a well-calibrated instrument at Low Earth Orbit (LEO) is a common method which has been widely used to assess the in-flight calibration of a new instrument. Different instruments on LEO spacecraft with similar spectral channels can be compared with each other using their simultaneous nadir observations (SNO). The postlaunch calibrations of Medium Resolution Spectral Imager (MERSI) and the Visible Infrared Radiometer (VIRR) in visible channels which are two major multi-spectral imaging radiometers onboard FY-3C are addressed based on SNO intercalibration method. Collection 6 reflectance products of AQUA MODIS are used as reference. The spectral difference impacts of matching channels are simulated and adjusted using GOME-2 hyperspectral measurements. As monitoring the stability of monthly forcing fits, it is found the linear fitting slopes of MERSI VIS channel 1~12 are scene reflectance dependence with relative differences greater than 20%, while the monthly forcing fits of VIRR show well agreement in VIS channels. This is proved to attribute to the nonlinear response of MERSI as the monthly measurements cover different dynamic ranges. A new radiometric calibration equation considering nonlinear correction is proposed based on an on orbit linear adjustment to prelaunch quadratic calibration. The new calibrations are more consistent with SNO samples, and greatly improve the performance over high reflective scene comparing with linear results verified by statistical measurements over Deep Convective Clouds targets. It is demonstrated that other reference is necessary in ocean color channels as MODIS reflectance is within 10% where the nonlinear feature is likely much serious. It is an invaluable lesson that the temporal variation of calibration slope not always indicates the detector’s degradation, but maybe is the valuable information that helps to expose undiscovered characters of instrument.

Fengyun-3C (FY3C) launched on 23 Sep, 2013 and InfraRed Atmospheric Sounder (IRAS) start to work on 30 Sep. Verification of instrument performance is an essential step before the L1 data distributed operationally. Verification performance including: BlackBody temperature, channel noises, radiance data assessment, Geo-location evaluation, instrument parameters trending, et al. Noise Equivalent Differential Radiance (NEdN) of all IR channels meet specification and got improvement on FY3B. IRAS L1 data are evaluated with Infrared Atmospheric Sounding Interferometer (IASI) measurements onboard European MetOp-A satellite using cross comparison method, biases are within 1K for all IR channels except ch1 and ch9. Trends of instruments components temperature are also discussed.

Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS) has been collecting global night light imaging data for more than 40 years. With the launch of Suomi-NPP satellite in 2011, the Day/Night Band (DNB) of the Visible Infrared Imaging Radiometer Suite (VIIRS) represents a major advancement in night time imaging capabilities because it surpasses DMSP-OLS in having broader radiometric measurement range, more accurate radiometric calibration, finer spatial resolution, and better geometric quality. DMSP-OLS sensor does not have on-board calibration and data is recorded as digital number (DN). Therefore, VIIRS-DNB provides opportunities to perform quantitative radiometric calibration of DMSP-OLS sensor. In this paper, vicarious radiometric calibration of DMSP-OLS at night under lunar illumination is performed. Events were selected when satellite flies above Dome C in Antarctic at night and the moon illuminates the site with lunar phase being more than quarter moon. Additional event selection criteria to limit solar and lunar zenith angle range have been applied to ensure no influence of stray light effects and adequate lunar illumination. The data from DMSP-OLS and VIIRS-DNB were analyzed to derive the characteristic radiance or DN for the region of interest. The scaling coefficient for converting DMSP-OLS DN values into radiance is determined to optimally merge the observation of DMSP-OLS into VIIRS-DNB radiance data as a function of lunar phases. Calibrating the nighttime light data collected by the DMSP-OLS sensors into radiance unit can enable applications of using both sensor data and advance the applications of night time imagery data.

An inter-calibration method of infrared channels of FY-3C MERSI and VIRR using NPP/CrIS and Metop/IASI as the hyperspectral reference sensor is introduced. Based on FY-3C SNO collocated samples with CrIS and IASI, on early orbit, we analyze the calibration biases of infrared bands of MERSI and VIRR. The results show that the brightness temperatures (BT) from the MERSI observation and CrIS have a good consistency, and the BT biases present an approximately normal distribution and the mean BT bias is about -0.18K with standard deviation of 0.83K. When the scene BT is lower than 250 K, the result of MERSI is higher than that of CrIS, while the result of MERSI is lower at the more than 250K scene. The BT from VIRR shows significant systematic bias with respect to CrIS and the mean BT bias is about -0.65 K (channel 4) and -0.72 K (channel 5) at 250K scene with standard deviation of 0.15 K and 0.12 K, respectively. Long term monitoring analysis demonstrates the above biases are stable in the early 6 months. The inter-calibration results using different hyperspectral sensors IASI and CrIS indicate the MERSI/VIRR biases with respect to two reference sensors have a good consistency and this further verifies the reliability of the method. It provides significant information to further correct the calibration biases of MERSI and VIRR.

The Global Change Observation Mission 1st – Water (CGOM-W1) or “SHIZUKU” was launched on May 18, 2012 (JST) from the JAXA’s Tanegashima Space Center. Subsequently, the GCOM-W1 satellite was joined to the NASA’s A-train orbit since June 29, 2012 to succeed observation by the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) and to provide combined utilization with other A-train satellites. The Advanced Microwave Scanning Radiometer 2 (AMSR2), which is a successor of AMSR-E, onboard GCOM-W1 has started its scientific observation since July 3, 2012. AMSR-E was halted its scientific observation on October 4, 2011, but has restarted observation in slow antenna rotation rate since December 4, 2012 for cross-calibration with AMSR2. AMSR2 has multi-frequency, total-power microwave radiometer systems with dual polarization channels for all frequency bands, and continues AMSR-E observations: 1) Water vapor, 2) Cloud liquid water, 3) Precipitation, 4) SST, 5) Sea surface wind speed, 6) Sea ice concentration, 7) Snow depth, 8) Soil moisture. JAXA opened the AMSR2’s brightness temperature products to the public since January 2013 after initial calibration/validation period by the GCOM-W1 Data Providing Service (https://gcomwl.jaxa.jp/). Thereafter, the retrieval algorithms of standard geophysical products for water vapor, cloud liquid water, precipitation, sea surface temperature, sea surface wind speed, sea ice concentration, snow depth and soil moisture were modified, and JAXA opened these standard geophysical products to the public since May 2013. In this paper, we present the present operation status of AMSR2.

GOSAT has been operated more than 5.5 years after its launch on January 23, 2009. Receiving TANSO-FTS Level 1A/1B data and TANSO-CAI Level 1A data from JAXA (FTS: Fourier Transform Spectrometer; CAI: Cloud and Aerosol Imager, JAXA: Japan Aerospace eXploration Agency), National Institute for Environmental Studies (NIES) has provided various kinds of Standard data products such as FTS SWIR Level 2 (XCO₂ and XCH₄: column concentrations of CO₂ and CH₄), FTS TIR Level 2 (vertical profiles of CO₂ and CH₄ concentration), FTS Level 4A (global CO₂ flux), FTS Level 4B (global CO₂ distribution), CAI Level 1B/1B+, and CAI Level 2 (cloud flag). After the latest updates of FTS Level 1 products to V161.160 (Version 161.160) by JAXA in 2013, now FTS SWIR Level 2 products are available as V02.21 (Version 02.21) for the entire period from April 2009 to May 2014. In March 2014, FTS Level 4 products of CO₂ (V02.02) were processed with FTS Level 2 (V02.21) for the period of June 2009 to October 2011. FTS Level 4 products of CH₄ (V01.01) were newly added to the Standard products and are available for 2 years from June 2009. FTS TIR Level 2 products (V01.0x) were updated in August 2014 and delivered to general users for 2.5 years from January 2010. There were some minor changes in their data format. After improving product search functions with an interactive map operation in GUIG (GUIG: GOSAT User Interface Gateway), general users are able to find and download these Standard products for their concerning area much easily.

Global Change Observation Mission, GCOM has two series of satellites, GCOM-W(Water) and GCOM-C(Climate). Both satellites are designed for five years on-orbit life time, and three satellites for each are planned to realize the long time over 11 years continuous global observation. The first satellite, GCOM-W with Advance Microwave Radiometer - 2 (AMSR-2), was already launched in 2012 and is continuously observing the earth for two years, now. The second satellite, GCOM-C with optical radiometer, Second Generation Global Imager (SGLI), is planned for launch in JFY- 2016. SGLI consists of two sensor units, Visible Near Infrared Radiometer (SGLI-VNR) and Infrared Scanning Radiometer (SGLI-IRS). The both flight model sensors are under the manufacturing and integration. This paper describes the SGLI-IRS development status.

Electro-Optical design of a push-broom space camera for a Low Earth Orbit (LEO) remote sensing satellite is discussed in this paper. An atmosphere analysis is performed based on ModTran algorithm and the total radiance of visible light reached to the camera entrance diameter is simulated by Atmosphere radiative transfer software PcModWin. Simulation is done for various conditions of sun zenith angles and earth surface albedos to predict the signal performance in different times and locations. According to the proposed simulation of total radiance incidence, appropriate linear CCD is chosen and then an optical design is done to completely satisfy electro-optics requirements. Optical design is based on Schmidt-Cassegrain scheme, which results in simple fabrication and high accuracy. Proposed electro-optical camera satisfies 5.9 meter ground resolution with image swath of higher than 23 km on the earth surface. Satellite is assumed to be at 681km altitude with 6.8km/s ground track speed.

GNSS-R has recently emerged as a new prosperous remote sensing tool in ocean surface, snow/ice surface and land surface. In this paper, the possible application in sensing the bare soil freeze-thaw process is investigated with GNSS-R. The Fresnel reflectivity from the wave synthesis technique is used to get the circular polarization reflectivity. Large differences are found for the Fresnel reflectivities at V, H, RR polarizations during bare soil freeze-thaw process, but there are almost no differences as for LR polarization. Therefore if a special GNSS-R receiver is designed, the reflected signals of RR polarization should be efficiently used. For GPS multipath reflectometry, the improved Fresnel reflectivity is inserted into the fully polarimetric forward multipath model to get the simulated GPS L1 observables: SNR, carrier phase multipath error and pseudorange code multipath error, which are used to estimate the bare soil freeze-thaw process. Compared to the thawed soil, the amplitudes of GPS observables are smaller for the frozen soil. Therefore, it is possible to monitor bare soil freeze-thaw process with ground geodetic GPS receivers.

Radiometric stability of the lunar surface and its smooth reflectance spectrum makes the moon an ideal target for calibrating satellite-based hyper/multi-band visible imagers, as demonstrated in several lunar calibration studies of satellite radiometers. Most of the lunar calibrations rely on using lunar irradiance models to calibrate satellite radiometers, which require the lunar irradiance model to be highly accurate. In this paper, we use Lunar Band Ratio (LBR) to trend satellite radiometer performance so that the usage of lunar irradiance model is not required. The LBR method is applied to monitor long term radiometric performance of VIIRS (Visible Infrared Imaging Radiometer Suite) onboard Suomi-NPP. VIIRS observes moon at nearly the same lunar phase angle through Earth view during scheduled spacecraft maneuver. Total lunar digital number are calculated for each VIIRS reflective solar bands (RSBs) from lunar observations and one of the most stable bands of VIIRS such as M4 band is chosen as the reference band for calculating the band ratio. LBRs are compared with the degradation factors derived from VIIRS operational radiometric calibration of RSBs using onboard solar diffuser. The LBR analysis reveals that M6 and M7 degrade the fastest and agree well with the trending independently determined from onboard solar diffuser. For stable bands such as M3-M4 of VIIRS, the variation range of band ratios of M2/M4 and M3/M4 are all within 0.6%, indicating the LBR can be used to reveal the sub percent band to band stability. For M11 band of VIIRS, there have been large uncertainties in verifying its radiometric performance using vicarious ground targets. LBR of M11 provides an independent and useful radiometric stability monitoring tool for verifying the relative stability of M11 band. The LBR analysis also shows that band-to-band variability in the spectrally similar band pairs such as I2 vs. M7 and I3 vs. M10 of VIIRS are consistent within 0.2%. It is demonstrated that long-term performance monitoring of VIIRS instrument using LBR is an important part of the VIIRS lunar calibration for solar bands and can effectively reveal the degradation of instruments.

The on-orbit calibration of the reflective solar bands (RSBs) of VIIRS and the result from the analysis of the up-to-date 3 years of mission data are presented. The VIIRS solar diffuser (SD) and lunar calibration methodology are discussed, and the calibration coefficients, called F-factors, for the RSBs are given for the latest reincarnation. The coefficients derived from the two calibrations are compared and the uncertainties of the calibrations are discussed. Numerous improvements are made, with the major improvement to the calibration result come mainly from the improved bidirectional reflectance factor (BRF) of the SD and the vignetting functions of both the SD screen and the sun-view screen. The very clean results, devoid of many previously known noises and artifacts, assures that VIIRS has performed well for the three years on orbit since launch, and in particular that the solar diffuser stability monitor (SDSM) is functioning essentially without flaws. The SD degradation, or H-factors, for most part shows the expected decline except for the surprising rise on day 830 lasting for 75 days signaling a new degradation phenomenon. Nevertheless the SDSM and the calibration methodology have successfully captured the SD degradation for RSB calibration. The overall improvement has the most significant and direct impact on the ocean color products which demands high accuracy from RSB observations.

Modulation transfer function (MTF) can be used to evaluate spatial quality of an satellite imaging sensor using a sharp edge, a pulse target, or bar pattern target. This investigation evaluates on-orbit MTF performance of FengYun (FY)-3C MERSI with 20 Bands with 1 km and 250 m spatial resolutions using polar ice and snow as a sharp edge, which was launched on September 23 of 2013. The MTF is calculated by using a Fourier transformation on the line spread function (LSF) though a simple differentiation of the edge spread function (ESF). The final MTF Nyqusit frequencies of the most of MERSI Bands along FY-3C flight direction are higher than 0.30, which are satisfy the original design requirements of 0.25 (250 m) and 0.27 (1km). But the Nyquist frequencies of all Bands along FY-3C scanning direction are around 0.13 that are clearly lower than 0.25/0.27. This relatively worse spatial quality of image along FY-3C scanning direction is primarily attributed to the 27% overlapped scan mode of MERSI sensor for every pixel. The objective of design defect in FY-3C MERSI instrument system is to enhance the signal-to-noise ratio (SNR) of scanning image. To overcome the drawback, in future, we will develop some deblurring methods to restore FY-3C/MERSI image along scanning direction.

The Advanced Land Observing Satellite-2 (ALOS-2) carries the phased array type Synthetic Aperture Rader (SAR) with the L-band frequency named PALSAR-2. ALOS-2 provides necessary data for disaster management, land and infrastructures management, resource management and so on. For disaster management by satellite based SAR, high resolution and wide swath width observation are needed. The Pulse Repetition Frequency (PRF) must be higher to improve azimuth resolution with less ambiguity caused by aliasing, but lower PRF is necessary to realize wider swath width. From this reason, high resolution and wide swath width are conflicting requirements for SAR. We have realized the requirements by adopting the multi-beam technology. PALSAR-2 has one transmitter and two receivers (dual beam system). This makes possible to reduce PRF and PALSAR-2 enables to receive the back scatterings, which are received in twice in the single beam receiver, at the same time. Therefore PALSAR-2 can realize high resolution and wide swath width capabilities by mean of the dual beam system. Improving resolution and swath width leads to increasing the data volume. Large amount of data need longer time to send the data to ground stations. From this reason the high speed data transmitting system with multi-mode X-band modulator has been developed. The modulator works with 800Mbps in 16QAM mode. This paper presents the initial on-orbit checkout result of ALOS-2.

The Second-generation Global Imager (SGLI) on the Global Change Observation Mission (GCOM) is a multi-band optical imaging radiometer in the wavelength range from near-UV to thermal infrared. SGLI will provide high accuracy measurements of Ocean, Atmosphere, Land and Cryosphere. SGLI consists of two radiometers, the Visible and Near Infrared Radiometer (VNR) and the Infrared Scanning Radiometer (IRS). This paper describes VNR Engineering Model (EM) and Proto Flight Model (PFM) optical test results. Especially we achieved measurement accuracy of ±4% for polarization rate and that of ±1.3deg for polarization direction that enables objective accuracy of aerosol observation.

Radiometric calibration is important for continuity and reliability of any optical sensor data. The Moderate Resolution Imaging Spectroradiometer (MODIS) onboard NASA EOS (Earth Observing System) Aqua satellite has been nominally operating since its launch on May 4, 2002. The MODIS thermal emissive bands (TEB) are calibrated using a quadratic calibration algorithm and the dominant gain term is determined every scan by reference to a temperature-controlled blackbody (BB) with known emissivity. On a quarterly basis, a BB warm-up and cool-down (WUCD) process is scheduled to provide measurements to determine the offset and nonlinear coefficients used in the TEB calibration algorithm. For Aqua MODIS, the offset and nonlinear terms are based on the results from prelaunch thermal vacuum tests. However, on-orbit trending results show that they have small but noticeable drifts. To maintain data quality and consistency, an iterative approach is applied to adjust the prelaunch based nonlinear terms, which are currently used to produce Aqua MODIS Collection-6 L1B. This paper provides details on how to use an iterative solution to determine these calibration coefficients based on BB WUCD measurements. Validation is performed using simultaneous nadir overpasses (SNO) of Aqua MODIS and the Infrared Atmospheric Sounding Interferometer (IASI) onboard the Metop-A satellite and near surface temperature measurements at Dome C on the Antarctic Plateau.

FY-2D is the second Geostationary Operational Meteorological Satellite of China and launched on December 08, 2006. With the launch of FY-2D, Chinese geostationary meteorological satellite observing system formatted of the first binary mode, greatly improving the timeliness of meteorological satellite cloud images. In this paper, the optical structure of the SVISSR onboard FY-2D was introduced. Some key optics on-orbit performances of FY-2D SVISSR were analyzed, including onboard blackbody and cold FPA. The onboard blackbody calibration models were set up and the methodologies were also introduced step by step. Base on the GSCIS calibration results, the model coefficients were determined. The historical FY-2D satellite data were also recalibrated with these models. Based on the comparisons of the calibration coefficients between onboard calibration models, cross calibration with AIRS and operational calibration coefficient in product, the conclusion can be drawn that the calibration results from blackbody models and cross calibration with AIRS were better than operational calibration results in product. The calibration results of blackbody models were agreed well to the cross calibration with AIRS, but the frequency of calibrations with blackbody models were much higher than cross calibration with AIRS. The onboard blackbody calibration models of FY-2D SVISSR based on GSICS can be used to calibrate the satellite infrared data operationally.

Calibration and validation (Cal and Val) is one of the most important quality assurance means for satellite payload performance and data quality which has actually restricted RS applicable scope. It has aroused various attentions from academia and industries in recent few decades. The challenges include the lack of consistent RS assessment standard, the uncertainties introduced by atmospheric effect, as well as the gaps in non-synchronous measurements between satellite and field observation. As one of the countries which launched the largest number of earth observation satellites/payloads in last five years, China engaged to solve various challenges of Cal and Val for quantitative RS applications. Several reprehensive works were introduced, including the development of remote sensing technology standardization, the stepwise Cal and Val system, China’s Baotou comprehensive Cal/Val site, automatic in-situ calibration exploration, etc. All these works mitigated the uncertainties of RS measurement and enhanced the precision of quantitative remote sensing.

Medium Resolution Spectral Imager (MERSI) is a keystone instrument onboard Fengyun-3 (FY-3), the second generation of polar-orbiting meteorological satellites in China. The first unit still in operation is FY-3A which was launched on May 27, 2008 in a sun-synchronous morning orbit with a local equator-crossing time of 10:30 AM in descending node. The second unit still in operation is FY-3B which was launched on November 5, 2010, in an afternoon orbit with an equator-crossing time of 1:30 PM in ascending node. FY-3 MERSI provides global coverage on top-of-atmosphere (TOA) radiances used for a broad range of scientific studies of the Earth’s system. Nineteen of the 20 MERSI spectral bands are reflective solar bands (RSBs) from 412 NM to 2130 nm, which cannot be absolutely calibrated onboard. The long-term on-orbit response changes of FY-3A/B MERSI are relatively large at visible bands. A multisite calibration tracking method has been developed to monitor the RSB radiometric response variation, revealing that the overall degradation for 412 nm of FY-3A MERSI is about 43% until June 2014. A daily calibration updating model is developed to recalibrate FY-3A/B MERSI, and the data quality is monitored using SNO targets against Aqua MODIS. This paper demonstrates the radiometric performance of FY-3A/B MERSI RSBs after recalibration accounting for the temporal variation of radiometric response. The recalibrated MERSI shows good agreement with MODIS. For FY-3B MERSI band 1 (470nm), the overall percentage difference (Mean±Std) is within 4%.

In order to realize unmanned vicarious calibration, Automated Test-site Radiometer (ATR) was developed for surface reflectance measurements. ATR samples the spectrum from 400nm-1600 nm with 8 interference filters coupled with silicon and InGaAs detectors. The field of view each channel is 10 ° with parallel optical axis. One SWIR channel lies in the center and the other seven VNIR channels are on the circle of 4.8cm diameters which guarantee each channel to view nearly the same section of ground. The optical head as a whole is temperature controlled utilizing a TE cooler for greater stability and lower noise. ATR is powered by a solar panel and transmit its data through a BDS (China’s BeiDou Navigation Satellite System) terminator for long-term measurements without personnel in site. ATR deployed in Dunhuang test site with ground field about 30-cm-diameter area for multi-spectral reflectance measurements. Other instruments at the site include a Cimel sunphotometer and a diffuser-to-globe irradiance meter for atmosphere observations. The methodology for band-averaged reflectance retrieval and hyperspectral reflectance fitting process are described. Then the hyperspectral reflectance and atmospheric parameters are put into 6s code to predict TOA radiance which compare with MODIS radiance.

To monitor changes in sensor performance and sensor calibration is a critical step to ensure data quality and to meet the needs of quantitative remote sensing in a broad range of scientific applications. One of the least expensive and increasingly popular methods of on-orbit calibration has been the use of large-area stable terrestrial sites. In this study, three stable desert sites of Libya-1, Sonora, and Arabia-2 are used to assessment the radiometric changes of reflective solar bands of FY-3A/MERSI from May 2008 to Dec. 2013. For each site, two BRDF models are established using the TOA reflectance measurements in the winter half-year and summer half-year late in the mission. Then, the degradation rates of RSBs of MERSI are predicted using an exponential fit of the BRDF-corrected time series. Results show that the use of two BRDF models is effective to removal of seasonal oscillation caused by angular effects. Degradation rates from three desert sites are in good agreement, with the standard deviation less than 1.5% for most of the bands. When compared with the DCC method, consistent detecting results are found, and the absolute deviation is less than 3% for most of the channels.

FY-3C/MERSI has some remarkable improvements compared to the previous MERSIs including better spectral response function (SRF) consistency of different detectors within one band, increasing the capability of lunar observation by space view (SV) and the improvement of radiometric response stability of solar bands. During the In-orbit verification (IOV) commissioning phase, early results that indicate the MERSI representative performance were derived, including the signal noise ratio (SNR), dynamic range, MTF, B2B registration, calibration bias and instrument stability. The SNRs at the solar bands (Bands 1–4 and 6-20) was largely beyond the specifications except for two NIR bands. The in-flight calibration and verification for these bands are also heavily relied on the vicarious techniques such as China radiometric calibration sites(CRCS), cross-calibration, lunar calibration, DCC calibration, stability monitoring using Pseudo Invariant Calibration Sites (PICS) and multi-site radiance simulation. This paper will give the results of the above several calibration methods and monitoring the instrument degradation in early on-orbit time.

Medium Resolution Spectral Imager (MERSI) is the key imaging sensor on board Fengyun-3 (FY-3), the second generation polar-orbiting meteorological satellites in China, currently operating on both FY-3A, FY-3B and FY-3C satellites. It has 20 spectral bands, including 19 reflective solar bands (RSBs) with center wavelengths from 0.41μm to 2.1μm and 1 thermal emissive band (TEB) with center wavelength 12μm, making observations at two spatial resolutions: 250 m (bands 1-5) and 1km (bands 6-20). The FY-3C has been launched in 23, Sept., 2013. The MERSI doesn't carry on-board calibration standards. To obtain RSBs radiometric responses, pre-launched field radiometric calibration test which is called Solar Radiation Based Calibration(SRBC) was taken in Dali in 27, Feb. to 2, Mar., 2013. For the SRBC measurement which the sun was the source of irradiance, MERSI viewed the reflected solar irradiance from a set of the sixteen reference spectral on panels with different reflective level. The uniformity, reflectivity and BRDF (Bidirectional reflection of distribution function) of sixteen reference panels were tested in advance. There are two kinds of calibration coefficient generation methods used in SRBC. One is similar as the Sea-WiFS pre-launch calibration method by Langley calibration. Besides this, we use a portable spectrometers produced by Analytical Spectral Devices inc. (ASD inc.) named FieldSpec 3 to measure the absolutely reflected radiance simultaneously. The calibrated spectrometers measured radiance could be as the reference radiance and the the calibration coefficient of the MERSI can be calculated. We called this method Calibration Based on Reference Instrument(CBRI). The results of these two methods are comparable. The CBRI results are less then 6% difference with Langley calibration method in most channels except water-vapor channels and channel 15. An non-linear feature of the most FY-3C/MERSI detectors was found for the first time. This phenomenon is even more obvious for the water-vapor channels. The second order coefficient determined by pre-launched calibration is quite useful to improve the on-obit calibration accuracy.

This study investigates the VIIRS reflective solar bands (RSB) calibration stability using the Deep Convective Clouds (DCC) technique. DCC time series from March 2012 to August 2014 were developed for bands M1-M5 and M7. The mean and mode of the monthly probability distribution functions of DCC reflectance are used as two important indices in using DCC for calibration. The DCC mode time series, which are more stable than the mean time series, were chosen for calibration stability monitoring for individual bands. For bands M5 and M7, our results indicate that the operational radiometric calibration stabilities (1-sigma) are 0.3% and 0.4%, respectively, with variations (maximum – minimum) less than 1.3%. The stabilities of bands M1-M4 are 0.5% - 0.7%, with variations of 2% -3.5%. Larger fluctuations in bands M1-M3 monthly DCC reflectance were observed since early 2014, consistent with F-factor trend changes during this period. The DCC mean band ratio time series were used for inter-channel relative calibration stability monitoring. M1/M4, M2/M4, M3/M4, and M5/M7 time series reveal distinct band ratio patterns in 2013 compared to those in 2012. The DCC time series were also compared with the VIIRS validation site time series and VIIRS-MODIS simultaneous nadir overpass time series. Comparison results further support that the DCC time series are capable to detect sub-percent calibration changes in the visible and near-infrared spectrum.

The MODerate-resolution Imaging Spectroradiometer (MODIS) is one of the primary instruments in the National Aeronautics and Space Administration (NASA) Earth Observing System (EOS). The first MODIS instrument was launched in December 1999 on-board the Terra spacecraft. MODIS has 36 bands, among which 27-30 are Long Wave Infrared (LWIR) PhotoVoltaic (PV) bands covering a wavelength range from 6.72 μm to 9.73 μm. It has been found that there is severe contamination in Terra band 27 from other three bands due to crosstalk of signals among them. The crosstalk effect induces strong striping in the Earth View (EV) images and causes large long-term drift in the EV Brightness Temperature (BT) in the band. An algorithm using a linear approximation derived from on-orbit lunar observations has been developed to correct the crosstalk effect for band 27. It was demonstrated that the crosstalk correction can substantially reduce the striping in the EV images and significantly remove the long-term drift in the EV BT. In this paper, it is shown that other three LWIR PV bands are also contaminated by the crosstalk of signals among themselves. The effect induces strong striping artifacts and large long-term drifts in these bands as similarly observed in band 27. The crosstalk correction algorithm previously developed is applied to correct the crosstalk effect. It is demonstrated that the crosstalk correction successfully reduces the striping in the EV images and removes long-term drifts in the EV BT in bands 28-30 as was done similarly for band 27. The crosstalk correction algorithm can thus substantially improve both the image quality and radiometric accuracy of the LWIR PV bands Level 1B (L1B) products. The algorithm can be applied to other MODIS bands and/or other remote sensors that exhibit an electronic crosstalk effect.

Using Global Space-based Inter-Calibration System (GSICS), the thermal infrared (TIR) channel was calibrated with high precision. During this procedure, a new calibration table was made, and the sensor non-linear effect was corrected. During the TIR channel image remapping and Level2 (L2) dataset generation procedure, the bilinear interpolation was widely used. Most of the L2 data was stored in D/N count with corresponding calibration table, which assumes D/N count is linear. But in the real world, the non-linear D/N count which comes from imprecise modeled A/D transformation of instrument sensor, will lead to the temperature bias on L2 dataset, even though the high precision calibration Look up Table (LUT) was regenerated. In this paper, D/N bias comes from the mapping process was diagnosed, with the consideration of the temperature difference between neighbor pixels.

Two satellites named HJ-1A and HJ-1B were launched on 6 September 2008, which are intended for environment and disaster monitoring and forecasting. The infrared scanner (IRS) onboard HJ-1B has one thermal infrared band. Currently, for sensors with one thermal band (e.g. Landsat TM/ETM+ and HJ-1B), several empirical algorithms have been developed to estimate land surface temperature (LST). However, surface emissivity and atmospheric parameters which are not readily accessible to general users are required for these empirical methods. To resolve this problem, particularly for HJ-1B, new retrieval methodology is desired. According to proper assumptions, two approaches were proposed, which included the single-channel method based on temporal and spatial information (MTSC) and the image based single-channel method (IBSC). The newly developed methods are mainly for estimating LST accurately from one thermal band, even without any accurate information related to the atmospheric parameters and land surface emissivity. In this paper, we introduce and give preliminary assessments on the new approaches. Assessments generally show good agreement between the HJ-1B retrieved results and the MODIS references. Especially, over sea and water areas the biases were less than 1K while the root mean square errors were about 1K for both MTSC and IBSC methods. As expected, the MTSC method did superiorly to the IBSC method, owning to spatiotemporal information is incorporated into the MTSC method, although more experiments and comparisons should be conducted further.

BRDF has numerous applications in on-orbit satellites vicarious calibration. The 2013 Dunhuang Gobi surface directional reflectance measurements experiment were held during Aug. 20 to Aug. 28. In order to match the spatial resolution (0.25-1.25km) of meteorological satellites, 3*3 sample points were selected covering the 10*10km area. All the data were measured during (3 hours before and after) the noon without taking into account the large sun zenith angle because of the lack of the satellite passing through. Totally 9 groups of directional reflectance (DREF) were measured by the use of ASD (350-2500nm), standard reference board and a portable DREF measurement system. At each point, DREF were measured by different observation zenith angle (0, 20, 40 and 60 degree) and azimuth angle (0, 45, 90, 135, 180, 225, 270, 315 and 360 degree) in 30 minutes. Different BRDF models were selected such as Walthall, Sine Walthall, Hapke, Roujean and Ross-Li. The model coefficients were derived corresponding to the observed data. The relative differences (RD) of the models with respect to the measured values were calculated. The accuracy of MCD43 products in the Julian day of 233 and 241 were also validated. Results showed that Ross-Li model had the smallest RD. The RD between the DREF from MCD43 products and the measured values were 10.26%(233) and 8.96% (241)@550nm, respectively.

Differential Interferometry Synthetic Aperture Radar (D-InSAR) is a hot-spot technology for detecting large-scale ground deformation, among which, two-pass D-InSAR is regarded as a classical algorithm. Two-pass D-InSAR is an algorithm with high stability and simple process flows, whose precision can always be influenced by the accuracy of DEM, spatial decoherence, and factors like that. Therefore, this paper introduces an improved two-pass D-InSAR algorithm to solve these problems: 1) apriori filters in azimuth direction is used to recover the spatial and temporal coherence; 2) three-level coregistration strategy is used to improve the matching precision. By comparing the vertical deformation chart with traditional two-pass D-InSAR process flow without the proposed two steps, it is proved that the improved algorithm has better stability and accuracy than traditional process flow, and has a good prospect in urban land subsidence detecting field in the future. Through the experiment, the land subsidence in the center area of Shanghai has been successfully detected using the improved two-pass D-InSAR algorithm which importing two images of Envisat/ASAR data from 2003 to 2005. Compared with ground level measuring data with the same spatial and temporal attributes that proved by statistic index (t-test method), the improved algorithm in this paper can give viable and reliable results. Combined with historical results inverted by InSAR technology, the land subsidence condition of Shanghai has rebounded and is accelerating again, which should be paid enough attention.

GOES-R Algorithm Working Group’s (AWG) Product Processing System Framework is currently being run both in operations and in near real-time to support algorithm verification and validation over extended seasonal datasets. The algorithms are being tested using a variety of data sets, including: MODIS, SEVIRI, GOES, VIIRS data, and ABI WRF simulated data. The Advanced Himawari Imager(AHI) data will also be used as ABI proxy data to test the GOES-R algorithms in the Framework. AWG Integration Team (AIT) has developed a suite of tools to monitor product quality, product processing, and system performance for the near real-time product generation. These capabilities have allowed the framework to be expanded for use in transitioning algorithms to operations. The GOES-R AWG Derived Atmospheric Motion Vector Winds algorithm has been successfully updated and transitioned to operations running on existing GOES and VIIRS data. Other GOES-R algorithms that are being upgraded for operational use on VIIRS include the Clouds, Aerosols, and Cryosphere products. In addition, legacy operational cloud systems will be integrated into the Framework. The design details of the AWG Framework, near real-time algorithm product generation system, monitoring tools, transitioning of the framework to operations, and future algorithm implementation plans shall be discussed.

Post-launch monitoring of radiometric accuracy and stability of VIIRS (Visible Infrared Imaging Radiometer Suite) Solar Reflective Bands (RSB) at high gain stage (HGS) is essential for ocean color applications. This study investigates the absolute radiometric calibration accuracy of VIIRS bands M1-M5 at HGS using selected clear-sky dark ocean surfaces where top of atmosphere (TOA) signal is dominated by Rayleigh scattering. Vicarious gains were estimated using ratios between satellite observed and radiative transfer model simulated TOA reflectance. VIIRS TOA reflectance was simulated using 6SV (Second Simulation of a Satellite Signal in the Solar Spectrum – Vector, version 1.1). Input parameters required by the 6SV, including atmospheric profiles, wind speed and direction, aerosol optical thickness, and chlorophyll-a concentration, were obtained from the NASA Modern-Era Retrospective Analysis for Research and Applications reanalysis products, VIIRS aerosol optical thickness product, and previous studies. The Rayleigh scattering method developed in this study was applied to June to August 2014 VIIRS observations over six oceanic sites. Preliminary results indicated that the 3-month averaged vicarious gain for bands M1, M2, and M5 are close to 1. Relatively larger vicarious gains were observed in the other two bands, especially in band M4. The Rayleigh scattering calibration results generally agree with results from the VIIRS deep convective clouds time series analysis.

Moon reflects sun light and its surface is radiometicly stable, making it an ideal target for calibrating satellite radiometers. Since lunar irradiance depends strongly on lunar phase and differs between waxing and waning phases, an accurate modeling of dependence of lunar irradiance on lunar phase angle is needed and requires long term consistent observations of the moon. Since its operation in 1998, the Visible and Infrared Scanner (VIRS) aboard the Tropical Rainfall Measuring Mission (TRMM) satellite makes regular observations of moon through space view for about 15 years with comprehensive coverage of lunar phases varying from waxing to waning. Two of these VIRS bands are reflected solar bands centered at 0.62 and 1.61um. Lunar measurements through space view of VIRS are not subject to atmospheric effects. Therefore, long term lunar observation by VIRS on TRMM is an invaluable dataset for both verifying and calibrating lunar irradiance models. In this study, analysis of long-term lunar observations using VIRS data are performed and phase-angle dependence of lunar irradiance is modeled. Effects of waxing and waning phases on lunar irradiance for two visible bands of VIRS are quantified. It is found that the lunar disk-integrated intensity of waxing lunar phase is higher than those of waning phase for phase angle >40° for both channels and is consistent with the fact that the waning moon shows more of dark maria. The derived phase angledependences of lunar disk effective reflectance for these two channels are compared with model.

Dynamic range and response linearity are two key parameters for impacting the quality of remote sensing image and subsequently the quantitative applications. Due to the space radiation and the degrading of electronic devices, the inflight dynamic range and response linearity of remote sensing payload are subject to change, and is essential to be assessed. Therefore, in this paper, with the aid of the permanent artificial target located in the AOE Baotou site in China, the two parameters for pan-chromatic camera (Pan) and the multi-spectral camera (Band 1-4) onboard GF-1 satellite are assessed with an extrapolation method using the in situ measurements and corresponding images acquired on November 4, 2013. The results show that the low point of the dynamic range for Pan band, Band 1, Band2, Band3 and Band4 is -24.08 W•sr-1m-2μm-1, -52.22 W•sr-1m-2μm-1, -35.20 W•sr-1m-2μm-1, -31.92 W•sr-1m-2μm-1, -24.07 W•sr-1m-2μm- 1 respectively; while the corresponding high point is 271.77 W•sr-1m-2μm-1, 401.58 W•sr-1m-2μm-1, 287.46 W•sr-1m- 2μm-1, 237.33W•sr-1m-2μm-1, 307.49W•sr-1m-2μm-1, respectively; meanwhile, it is demonstrated that all the sensors have a response linearity error of lower than 1%. Moreover, an analysis for this assessment is performed in terms of the uncertainties for surface reflectance measurement (1%), aerosol optical depth (10%), column water vapor (10%), MODTRAN model (1%) and solar irradiance (1%) using a simulation method with the aid of MODTRAN 4.0 model, and a total uncertainty of 2.12% is acquired.

Ocean surface wind vectors (OVW) from scatterometers have been proved to be of great benefit to marine weather analysis and numerical model prediction. Conventional single-frequency scatterometers are capable to measure substantially accurate wind fields in clear atmospheric conditions, whereas winds obtained in marine extreme weather conditions are not so satisfying due to the high wind speed saturation effect and the rain perturbation. Therefore, a dualfrequency wind field measuring radar (WIFIR) to be onboard FengYun-3E is being predesigned to obtain relatively accurate wind fields in all weather conditions, which will compensate for the single-frequency shortcomings. The purpose of this study was to investigate the potential ability of WIFIR to measure OVW in tropical cyclones. A high-fidelity forward model was developed to simulate the sea surface normalize radar cross sections (NRCS) measured by WIFIR. The wind and rain rate fields used to drive the model are generated by UWNMS cloud model for Hurricane Ivan in 2004. High-wind GMFs and a theoretical rain model, which includes attenuation and volume scattering effect, have been utilized to describe the forward model. Based on the simulation results, the impact of rain on radar measurements and a dual-frequency retrieval algorithm were studied. The dual-frequency method was shown to have the ability to obtain information of rain rates up to 30mm/hr, and acquire more accurate wind vectors than single-frequency measurements. This method will be more effective to improve wind retrieval accuracy in tropical cyclones with the synchronous observation of microwave humidity sounder (MWHS) aboard FY-3 satellite.

Spaceborne microwave scatterometers have successfully provided global ocean surface wind field for two decades. However current scatterometers still cannot satisfy the requirement of achieve ocean wind vectors in nearly all weather and all wind conditions. A new microwave scatterometer - the WindRadar with dual frequency onboard Chinese FengYun-3E meteorological satellite is being developed to attempt to overcome their shortcomings. This paper introduces the objectives of the WindRadar, then describes the design of its some key system characteristics, and the performance of the WindRadar is also analyzed at the end.

When observing unchanging targets or slow-changing targets, a rotating array can be used instead of a stationary array in an interferometric radiometer to reduce the complexity and the cost. The configuration of a stationary array determines its coverage in spatial frequency domain. But for a rotating array, the baselines were distributing on a series of concentric circles with radiuses of the baseline lengths, no matter what its configuration was. According to the characteristics of the distribution of the baselines, the expressions of system sensitivity and spatial resolution of a rotating interferometric radiometer were deduced in thwas paper. For a rotating interferometric radiometer with big synthetic aperture, like the Geostationary Interferometric Microwave Sounding (GIMS) prototype, it was very difficult to find a suitable calibration source to measure the system sensitivity. Therefore, the system sensitivity of the GIMS prototype was estimated based on the sensitivity of all channels by the sensitivity formula. Since the array factor of an interferometric radiometer was the pulse response of a point target, the spatial resolution of the GIMS prototype obtained by imaging an artificial quasi point target was used to demonstrate the formula in this paper, and the results were nearly identical. In addition, some different window functions were used to weight visibility samples of the prototype, and their effects on the sensitivity and the spatial resolution were analyzed. The principle of selecting the weighted window was described at the end.

The Visible Infrared Imaging Radiometer Suite (VIIRS) is one of the key instruments onboard the Suomi NPP spacecraft. To ensure the data quality of the VIIRS for all users and products, and to support the calibration/validation of the VIIRS, a calibration knowledgebase has been developed as part of the cal/val tool for the postlaunch verification and validation of VIIRS SDR and its use for data quality assurance, anomaly investigation, and EDR applications. The components of the knowledge-base include 1) event log database which keeps record of all major changes and activities in both spacecraft flight, and ground processing system, including such events as lunar maneuvers, calibration updates and anomalies in the processing systems, and instrument performance anomalies such as scan sync loss; 2) VIIRS image gallery, which has a large sample of VIIRS images for areas of interest such as hurricanes, solar eclipse; 3) validation site time series which provides long term trending at more than 30 vicarious sites worldwide; 4) daily orbital track which is used for locating data granules based on the time, location, and orbit. In addition, all VIIRS related parameters and information are also provided. The Calibration Knowledge base has become an indispensable tool for VIIRS data users. The URL for the VIIRS Calibration Knowledge Base is http://ncc.nesdis.noaa.gov.

A Rotating fan-beam scatterometer (RFSCAT), which provides a set of different incidence and azimuth angle combinations and wide continuous swath coverage, will be flown on the Chinese-French Oceanography Satellite (CFOSAT). In this paper, a pre-processing algorithm is developed to estimate the backscatter coefficient (σ⁰) of RFSCAT, which includes the procedures of system distortion correction, thermal noise removal, internal signal calibration, and elimination of the observing geometry effects. The algorithm is then tested using the experimental data from an airborne campaign. The estimated σ⁰ are consistent with Nscat-2 geophysical model function (GMF), indicating that the pre-processing chain acts well for RFSCAT.

SAR image despeckling is an active research area in image processing due to its importance in improving the quality of image for object detection and classification.In this paper, a new approach is proposed for multiplicative noise in SAR image removal based on nonlocal sparse representation by dictionary learning and collaborative filtering. First, a image is divided into many patches, and then a cluster is formed by clustering log-similar image patches using Fuzzy C-means (FCM). For each cluster, an over-complete dictionary is computed using the K-SVD method that iteratively updates the dictionary and the sparse coefficients. The patches belonging to the same cluster are then reconstructed by a sparse combination of the corresponding dictionary atoms. The reconstructed patches are finally collaboratively aggregated to build the denoised image. The experimental results show that the proposed method achieves much better results than many state-of-the-art algorithms in terms of both objective evaluation index (PSNR and ENL) and subjective visual perception.

Reliable and accurate Digital Building Model (DBM) generation is essential for many applications that involve in using of digital 3-D city models. This paper focuses on the integration of LiDAR and multiple aerial image data for accurate generation of DBM in urban areas. First, the LiDAR data are segmented to derive rough building boundaries, which are projected onto the multiple aerial photos to building a buffer area for each building in the proceeding procedures. Second, straight line segments are detected in the buffer area, respectively Then, straight line matching in 3D planar patch are conducted on multiple images so as to derive 3d matched lines in the planar patch to compete for the correct boundary as many as possible. Several constraints are taken into consideration in the process of matching. Finally, a similarity measure is defined to select one straight line segment which is believed to represent the building boundary. Afterwards, a closed polygon is generated for each concerned building. The proposed methodology is implemented using real datasets, and the experimental results show that the integration of LiDAR and multiple aerial photos is promising for digital building model generation.

The 36 MODIS spectral bands, with wavelengths ranging from 0.41 μm to 14.2 μm, are distributed on four focal plane assemblies: visible (VIS), near-infrared (NIR), short- and mid-wave infrared (SMIR), and long-wave infrared (LWIR). The MODIS reflective solar bands (RSB) are calibrated onorbit using a solar diffuser (SD), with its reflectance degradation monitored using a solar diffuser stability monitor (SDSM). The Terra MODIS SD degradation at 0.936 μm, as measured by the SDSM, is 2.4% after 14 years on-orbit. The Aqua MODIS SD degradation at 0.936 μm is 0.6% after 12 years on-orbit. The SWIR bands with spectral wavelengths centered at 1.24 μm (band 5), 1.37 μm (band 26), 1.64 μm (band 6), and 2.13 μm (band 7), are beyond the SDSM wavelength coverage (0.412 μm to 0.936 μm). Consequently, the gain of the SWIR bands is computed without factoring in the possible degradation of the SD. A technique to monitor the long-term stability of the MODIS SWIR bands is developed using pseudo-invariant desert targets. Results indicate a long-term drift of up to 1.5% of band 5 of Terra MODIS. The long-term stability of other Terra MODIS SWIR bands is seen to be within 0.5%. Similar results for Aqua MODIS indicate no observable drift, with changes within 0.5%. An implementation strategy to account for this correction in the MODIS Level 1 B (L1B) is also discussed.

All the star trackers must be composed of a baffle system to removes stray lights intensity. According to the mission, some external sources can illuminate the optical system and introduce some noises in the final image. The performance of a star tracker is often limited by the stray light level on the detector. Some familiar formulas for baffle system design that have already been introduced are somewhat useless due to some fundamental problems. In this paper, a complete analytical method is developed to fully design a two-stage baffle system. Furthermore, some new relationships are introduced to determine vane positions and heights. Finally, ray tracing performance analyses are performed to prove the formulation. The designed baffle simulations reveal that the attenuation factors are on the order of 109 for angles larger than the pre-defined exclusion angle.

PMOD/WRC is building the Compact and Light-weight Absolute RAdiometer (CLARA) to fly on the Norwegian Space Centre’s (NSC) NORSAT-1 mission. The CLARA is based on a new design by PMOD/WRC which minimizes size and weight while improving the radiometric performance. The NORSAT-1 mission is planned to be launched to a polar LEO in Q4 2015. The nominal mission duration is three years but NSC intends to operate NORSAT-1 for long as the platform and payload remain functional.

Due to a software error, the solar and lunar vectors reported in the on-board calibrator intermediate product (OBC-IP) files for SNPP VIIRS are incorrect. The magnitude of the error is about 0.2 degree, and the magnitude is increasing by about 0.01 degree per year. This error, although small, has an effect on the radiometric calibration of the reflective solar bands (RSB) because accurate solar angles are required for calculating the screen transmission functions and for calculating the illumination of the Solar Diffuser panel. In this paper, we describe the error in the Common GEO code, and how it may be fixed. We present evidence for the error from within the OBC-IP data. We also describe the effects of the solar vector error on the RSB calibration and the Sensor Data Record (SDR). In order to perform this evaluation, we have reanalyzed the yaw-maneuver data to compute the vignetting functions required for the on-orbit SD RSB radiometric calibration. After the reanalysis, we find effect of up to 0.5% on the shortwave infrared (SWIR) RSB calibration.

Ultraviolet (UV) sensors on a geostationary orbit (GEO) have important potential value in atmospheric remote sensing, but the satellites orbit mode of it is quit different from sun-synchronous orbit satellites, which result in the significant diurnal and seasonal variations in radiation environment of earth observation and radiation signal of sensors, therefore, the effect to sensor radiometric performance, such as signal to noise ratio for atmospheric ultraviolet remote sensing caused by variations of solar angle is significant in the performance design of sensors. The synthetic ultraviolet sensor is set at the geostationary orbit, 36000 km away from the sea level of the Equator with 8.75 degree field of view, and the subsatellite track point of which is located at 90 degrees east longitude and Equator. The Satellite scanning angles (SA) from 0 to 8.648 degree that cover the earth surface are selected corresponding to the 10 degrees equal interval view zenith angle, and the SA from 8.648 to 8.785 degree cover the earth lamb 100 km far away from earth tangent point. Based on the MODTRAN4 model, on normal atmospheric conditions, the distributions of the UV upwelling radiance from surface or limb viewing path of the earth could be simulated with the change of sun's right ascension. Moreover, the average signal to noise ratio to the atmospheric sounding is obtained in different UV spectra using the Sensor signal to noise ratio model. The results show that the thresholds range, tendency and shape of signal to noise ratio have a variety of features affected by variation of Sun hour angles and declinations. These result and conclusions could contribute to performance design of UV sensors on the geostationary orbit.

Due to the complex launch condition, dynamic space environment, and up to 0.1" high-resolution imaging requirements, automatic focus (AF) technology in orbit has become one of the key technologies to obtain high-quality images for high-resolution imaging satellite, especially for the long focal length, large diameter optical remote sensor. This paper analyzes the focusing criterion theory of the smallest image entropy. For high-resolution optical imaging satellites, we have proposed innovatively an AF method based on configuration entropy focusing criterion. Data show that configurational entropy focusing criterion is more suitable for low-contrast celestial observation targets. For diffraction limited focal ratio and space optical remote sensor with F^#=39, focal length detection sensitivity reaches 0.1mm. Configurational entropy focusing technology improves the efficiency of image processing 2^2k times, which dramatically reduces the number of focusing movements. Adaptive AF with high speed and high precision satisfies imaging requirements of low-contrast targets for space exploration.