Advanced Spaceborne Thermal Emission and Reflection Radiometer
ASTER Advanced Spaceborne Thermal Emission and Reflection Radiometer Terra Launch from VAFB Terra Orbit Parameters
OrbitSun Synchronous Descending Node Time of Day10:30 am Altitude705 km Inclination98.2o Repeat Cycle16 days ASTER Instrument Overview
ASTER is an international effort: Japanese government is providing the instrument under METI (Ministry of Economy, Trade and Industry) and is responsible for Level 1 data processing Flies on NASAs Terra platform Science team consists of Japanese, American and Australian scientists ASTER Characteristics
Wide Spectral Coverage 3 bands in VNIR(0.52 0.86 m) 6 bands in SWIR (1.6 2.43 m) 5 bands in TIR(8.125 m) High Spatial Resolution 15m for VNIR bands 30m for SWIR bands 90m for TIR bands Along-Track Stereo Capability B/H 0.6 DEM Elevation accuracy: m (3) DEM Geolocation accuracy: 50m (3) Terra ASTER ASTER Bands ASTER Spectral Bandpass Baseline Performance Requirements ASTER Characteristic Functions
Item VNIR SWIR TIR Scan Pushbroom Whiskbroom Reflective (Schmidt) Refractive Reflective (Newtonian) D=82.25 mm (Nadir) D=190 mm D=240 mm D=94.28 mm (Backward) Dichroic and band pass filter Si-CCD PtSi-CCD HgCdTe (PC) 5000 x 4 2048 x 6 10 x 5 Cryocooler (Temperature) not cooled Stirling cycle, 77 K Stirling cycle, 80 K Telescope rotation Pointing mirror rotation Scan mirror rotation + 24 deg. deg. Cold plate and Radiator 2 sets of Halogen lamps Blackbody and monitor diodes K Thermal control Calibration method Telescope optics Spectrum separation Band pass filter Focal plane (Detector) Cross-track pointing ASTER Observation Modes
Subsystem Data Rate (Mbps) VNIR SWIR TIR Daytime Full Mode 89.2 VNIR Mode -- 62.0 Stereo Mode 31.0 TIR Mode 4.1 Nighttime S+T Mode 27.2 ASTER Cross-Track Pointing
EOS AM-1 Orbit Interval:172 km on the equator ASTER Imaging Swath: km Fixed 7 Pointing Positions + Arbitrary Pointing (rare cases) Total Coverage in Cross-Track Direction by Pointing Full Mode:232 km(+116 km / degrees) Recurrent Period:16 days (48 days for average) VNIR :636 km(+ 318 km / +24 degrees) Recurrent Pattern: days(4 days average) Comparison between ASTER Recurrent Period (day)
and the other imagers Terra ASTER JERS-1 OPS Landsat ETM SPOT HRV Spectral Bands VNIR: 3 3 4 SWIR: 6 2 TIR: 5 1 Stereo Capability Along-track B/H = 0.6 B/H = 0.3 Multi-orbit B/H: up to 1.0 Spatial Resolution (m) VNIR: 15 18 x 24 30 (15) 20 (10) SWIR: 30 30 TIR: 90 60 Pointing Angle VNIR: +24 +27 SWIR: +8.55 TIR: +8.55 Swath (km) 75 185 Recurrent Period (day) 16 44 26 Conversion of DN to Radiance
(Level-1A) DN values can be converted to radiance as follows. L = A V /G + D (VNIR and SWIR bands) L = AV + CV2 + D (TIR bands) Where L: radiance (W/m2/sr/m) A: linear coefficient C: nonlinear coefficient D: offset V: DN value G: gain For TIR, radiance can be converted into brightness temperature using Planks Law as shown below. i : the wavelength TBB : the brightness temperature C1 = x (W cm-2 m4) C2 = x (m K) (Fujisada, 2001 Level-1B Data Product The Level-1B data product can be generated by applying the Level1A coefficientsfor radiometric calibration and geometric resampling. Map projection : UTM, LCC, SOM, PS, Lat/Long Resampling : NN, BL, CC The geolocation field data are included in the Level-1B data to know the pixel position (latitude/longitude) on the ground. (Fujisada, 2001 Conversion of DN to Radiance (Level-1B)
Radiance value can be obtained from DN values as follows; Radiance = (DN value -1) x Unit conversion coefficient Unit conversion coefficients, which is defined as radiance per 1DN, are used to convert from DN to radiance. The unit conversion coefficient will be keptin the same values throughout mission life. (Fujisada, 2001 Band-to-band Registration Accuracy for Level-1B Data
Band-to-band Registration Accuracy for Level-1B Data Band-to-band Registration Errors Pixel Geolocation Knowledge Within Each Telescope Among Telescopes Relative Absolute SWIR/VNIR TIR/VNIR ver. 1.02 < 0.2 pixels < 0.5 pixels < 15 m < 50 m ver. 2.0 < 0.1 pixels SNRs Measured in Actual Data
212 > 54 9 213 > 70 8 177 7 181 6 5 Onboard lamp data (the minimum values for Lamp-A, higher than the specified input radiance) 218 > 140 4 SWIR 136 3N 200 2 (slightly lower than the specified input radiance) 224 1 VNIR Remarks Measured Value Specified Band # Subsystem ASTER Gain Settings Gain Normal High Low-1 Low-2 VNIR 1.0 2.5 or 2.0
0.75 N/A SWIR 2.0 0.12 0.18 Detection of High Temperature Targets SWIR Band # 4 5 6 7 8 9 Saturation Radiance (W/m2/sr/um) 73.3 103.5 98.7 83.8 62.0 67.0 Highest Temperature (deg. C.) 466 (739K) 385 (658K) 376 (649K) 358 (631K) 330 (603K) 326 (599K) ASTER Science Team Selects algorithms for higher level standard products Produces software for standard products Conducts joint calibration and validation exercises Conducts mission operations, scheduling, and mission analysis ASTER Calibration Activities
1. Onboard Calibration Devices VNIR: Halogen lamp + photodiode monitor (dual units) SWIR: Halogen lamp + photodiode monitor (dual units) TIR : Variable temperature blackbody (BB) 2. Onboard Calibration (OBC) (1) Long-term calibration: Every 17 days ( Every 33 days) VNIR, SWIR: Halogen lamp + earth night side observation TIR: BB temperature changed from 270 K to 340 K (2) Short-term calibration: Before each TIR observation TIR: BB temperature fixed at 270 K 3. Vicarious Calibration (VC) VNIR, SWIR: Ivanpah Playa, Railroad Valley Playa, Tsukuba, etc. TIR: Lake Tahoe, Salton Sea, Lake Kasumigaura, etc. VNIR In-flight Calibration Trend SWIR In-flight Calibration Trend ASTER Instrument Operations
ASTER has a limited duty cycle which implies decisions regarding usage must be made Observation choices include targets, telescopes, pointing angles, gains, day or night observations Telescopes capable of independent observations and maximum observation time in any given orbit is 16 minutes Maximum acquisitions per day Acquired~750 Processed~330 Science Prioritization of ASTER data acquisition
NASA HQ, GSFC, and METI have charged the Science Team with developing the strategy for prioritization of ASTER data acquisition Must be consistent with EOS goals, the Long Term Science Plan, and the NASA-METI MOU Must be approved by EOS Project Scientist Global Data Set A one-time acquisition
All land surfaces, including stereo Maximize high sun Optimal gain Consists of pointers to processed and archived granules which: Meet the minimum requirements for data quality Are the best acquired satisfying global data set criteria Science Team has prioritized areas for acquisition (high, medium and low) Regional Data Sets Focus on specific physiographic regions of Earth, usually requiring multi-temporal coverage Acquisitions are intended to satisfy multiple users, as opposed to specific requirements of individual investigator or small team Defined by the ASTER Science Team in consultation with other users (e.g., EOS interdisciplinary scientists) Science team provides prioritization (relative to other regional data sets) on a case-by-case basis Targeted Observations
Targeted observations are made in response to Data Acquisition Requests (DARs) from individual investigators or small groups for specific research purposes Japanese Instrument Control Center (ICC) does prioritization of DAR based on guidelines provided by Science Team Targeted observation may also be used to satisfy the global data set or regional data set acquisition goals, where appropriate ASTER Operation Complexity
Data Acquisition Based Upon Users Requests Instrument Operation Constraints (1) Data Rate Maximum average data rate:8.3 Mbps Peak data rate: Mbps (2) Power Consumption (3) Pointing Change 3. Selection of Operation Mode / Gain Settings 4. Utilization of Cloud Prediction Data Duty Cycle : 8% Automatic Generation of Data Acquisition Schedule ASTER US-JAPAN Relation
Terra ASTER Sensor TDRS Downlink ATLAS Science data Engineering data Telemetry data Uplink Command Direct Downlink TDRSS Japan US data Level-0 data DRS Expedited Data Set ASTER GDS Telemetry data EOSDIS Activity Product Product DAR, DPR DAR, DPR Product Data Processing/Analysis (Level 0Level 1) (High Level Product) Mission Operation (Observation Scheduling) Data Archive/Delivery User User Pacific Link ASTER Standard Data Products ASTER Primary Objectives
To improve understanding of the local- and regional-scale processes occurring on or near the earths surface. Obtain high spatial resolution image data in the visible through the thermal infraredregions. Why? Actually, ASTER-that Im gonna present here-is the only high spatial resolution instrument on the TERRA platform. The other sensors monitor the earth at moderate to coarse spatial resolutions.For those, ASTER will serve as a 'zoom' lens.So ASTER can be saidto be the core sensor of those five. (1) To promote research into geological phenomena of tectonic surfaces and geological history through detailed mapping of the Earths topography and geological formations.(This goal includes contributions to applied research in remote sensing.) (2) To understand distribution and changes of vegetation. (3) To further understand interactions between the Earths surface and atmosphere by surface temperature mapping. (4) To evaluate impact of volcanic gas emission to the atmosphere through monitoring of volcanic activities. (5) To contribute to understanding of aerosol characteristics in the atmosphere and of cloud classification. (6) To contribute to understanding of the role coral reefs play in the carbon cycle through coral classification and global distribution mapping of corals. ASTER is the zoom lens of Terra! ASTER Web Site: APPLICATIONS Surface Energy Balance Geology Wild Fires
Urban Monitoring Glacial Monitoring Volcano Monitoring Wetland Studies Land Use Surface Energy Balance Surface Energy Balance from ASTER data
El Reno OK, 4-Sep-2000, Kustas & Norman 2-source model ASTER data of El Reno OK, 4-Sep-2000: NDVI & Surface Temperature Geology 3 2 1 3 2 1 DST 4 6 8 DST DST Wild Fires Hayman Fire, Colorado June 16, 2002 ASTER bands as RGB Urban Monitoring Eiffel Tower Arc de Triomphe Louvre La Defense
Major cultural landmarks easy to see La Defense Glacial Monitoring Global Land Ice Measurements from Space
View from top of Llewellyn Glacier, British Columbia Goal is to determine the extent of worlds glaciers and the rate at which they are changing. Acquire global set of ASTER images Map global extent of land ice Analyze interannual changes in length, area, surface flow fields Volcano Monitoring January 2002 Eruption of Nyiragongo Volcano, Congo
Nyiragongo erupted January 17, 2002 sending streams of lave through the town of Goma. More than 100 people were killed. This perspective view combines ASTER thermal data (red) showing the active lava flows and lava in the crater; Landsat Thematic Mapper image, and Shuttle Radar Topography Mission digital elevation data. Wetland Studies Sediment Image Temperature Image
Sediment image is B1 color coded, T image is b12 color-coded. Land is masked out in both Land Use US-Mexico border at Mexicali
Note major irrigatin differences across border, field sizes, shapes, etc How Do I Get ASTER Data? Browse the archive: use the EOS Data Gateway (EDG) to find what data have already been acquired. Order data products desired: Submit a Data Acquisition Request: First become an authorized user; then request satellite obtain your particular data