ASTERAdvanced Spaceborne Thermal Emission and Reflection Radiometer

Terra Launch from VAFB

Terra Orbit Parameters

Orbit Sun Synchronous Descending Node

Time of Day 10:30 am

Altitude 705 km

Inclination 98.2o

Repeat Cycle 16 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 NASA’s Terra platform– Science team consists of Japanese,

American and Australian scientists

ASTER Characteristics

• Wide Spectral Coverage 3 bands in VNIR (0.52 – 0.86 μm)

6 bands in SWIR (1.6 – 2.43 μm) 5 bands in TIR (8.125 – 11.65 μm)

• High Spatial Resolution15m for VNIR bands

30m for SWIR bands90m for TIR bands

• Along-Track Stereo Capability B/H 0.6 DEM Elevation accuracy: 15m (3σ) DEM Geolocation accuracy: 50m (3σ)

Terra

ASTER

ASTERASTER Bands

ASTER Spectral Bandpass

Baseline Performance Requirements

Subsystem Band No.

Spectral Range (m)

Radiometric Resolution

Absolute Accuracy

()

Spatial Resolution

Signal Quantization

Levels

1 0.52 - 0.60 VNIR 2 0.63 - 0.69 NE < 0.5 % < + 4 % 15 m 8 bits

3N 3B

0.78 - 0.86 0.78 -0.86

4 1.600 - 1.700 NE < 0.5 % 5 2.145 - 2.185 NE < 1.3 %

SWIR 6 2.185 - 2.225 NE < 1.3 % < + 4 % 30 m 8 bits 7 2.235 - 2.285 NE < 1.3 % 8 2.295 - 2.365 NE < 1.0 % 9 2.360 - 2.430 NE < 1.3 % 10 8.125 - 8.475 < 1K 11 8.475 - 8.825 (270-340K)

TIR 12 8.925 - 9.275 NET < 0.3 K < 2K 90 m 12 bits 13 10.25 - 10.95 (240-270K) 14 10.95 - 11.65 (340-370K)

< 3K (200-240K)

ASTER Characteristic Functions

Item VNIR SWIR TIR

Scan Pushbroom Pushbroom WhiskbroomReflective (Schmidt) Refractive Reflective (Newtonian)D=82.25 mm (Nadir) D=190 mm D=240 mm

D=94.28 mm (Backward)

Dichroic and

band pass filterSi-CCD PtSi-CCD HgCdTe (PC)

5000 x 4 2048 x 6 10 x 5Cryocooler (Temperature) not cooled Stirling cycle, 77 K Stirling cycle, 80 K

Telescope rotation Pointing mirror rotation Scan mirror rotation

+ 24 deg. + 8.55 deg. + 8.55 deg.Cold plate Cold plate

and and

Radiator Radiator2 sets of Halogen lamps 2 sets of Halogen lamps Blackbody

and monitor diodes and monitor diodes 270 - 340 K

Thermal control Radiator

Calibration method

Telescope optics

Spectrum separation Band pass filter Band pass filter

Focal plane (Detector)

Cross-track pointing

Observation Mode

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

TIR Mode -- -- 4.1

S+T Mode -- 27.2

ASTER Observation Modes

EOS AM-1 Orbit Interval : 172 km on the equator ASTER Imaging Swath : 60 km

　　　　　 Fixed 7 Pointing Positions 　　 + Arbitrary Pointing (rare cases)

Total Coverage in Cross-Track Direction by Pointing

Full Mode : 232 km (+116 km / +8.55 degrees) Recurrent Period : 16 days (48 days for average)

VNIR : 636 km (+ 318 km / +24 degrees) Recurrent Pattern : 2-5-2-7 days (4 days average)

ASTER Cross-Track Pointing

Comparison between ASTER and the other imagers

Terra ASTER JERS-1 OPS Landsat ETM SPOT HRV

Spectral Bands VNIR: 3 3 4 3

SWIR: 6 4 2

TIR: 5 1

Stereo Capability

Along-track

B/H = 0.6

Along-track

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 18 x 24 30

TIR: 90 60

Pointing

Angle

VNIR: +24 +27

SWIR: +8.55

TIR: +8.55

Swath (km) 60 75 185 60

Recurrent Period (day)

16 44 16 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/µm)A: linear coefficientC: nonlinear coefficientD: offsetV: DN valueG: gain

For TIR, radiance can be converted into brightness temperature using Plank’s Law as shown below.

L(,T ) C1

5

1

exp(C2

T) 1

i : the wavelengthTBB : the brightness temperatureC1 = 3.7415 x 104 (W cm-2 µm4)

C2 = 1.4388 x 104 (µm K)

(Fujisada, 2001 ）

Level-1B Data Product

• The Level-1B data product can be generated by applying the Level1A coefficients for 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 ）

Level-1B Data Procuct

Data Directory

Generic Header

Ancillary Data

VNIR Data

SWIR Data

TIR Data

VNIR Specific Header

VNIR Band 1 VNIR Band 2 VNIR Band 3N VNIR Band 3B

VNIR Supplement Data

SWIR Specific Header

SWIR Band 4 SWIR Band 5 SWIR Band 6 SWIR Band 7 SWIR Band 8 SWIR Band 9

VNIR Image Data

SWIR Image Data

SWIR Supplement Data

TIR Specific Header

TIR Band 10 TIR Band 11 TIR Band 12 TIR Band 13 TIR Band 14

TIR Supplement Data

TIR Image Data

Geolocation Field Data

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 kept in the same values throughout mission life.

Unit Conversion Coefficient (W/(m2•sr•µm)/DN)

No. High gain Normal gain Low gain 1 Low gain 2

1 0.676 1.688 2.25

2 0.708 1.415 1.89 N/A

3N 0.423 0.862 1.15

3B 0.423 0.862 1.15

4 0.1087 0.2174 0.29 0.29

5 0.0348 0.0696 0.0925 0.409

6 0.0313 0.0625 0.083 0.39

7 0.0299 0.0597 0.0795 0.332

8 0.0209 0.0417 0.0556 0.245

9 0.0159 0.0318 0.0424 0.26510 6.882 x 10 -3

11 6.780 x 10 -3

12 N/A 6.590 x 10 -3 N/A N/A13 5.693 x 10 -3

14 5.225 x 10 -3

(Fujisada, 2001 ）

Band-to-band Registration Accuracy for Level-1B Data

Band-to-band

Registration Errors

Pixel Geolocation

Knowledge

Within Each

Telescope

Among Telescopes

Relative AbsoluteSWIR/VNIR TIR/VNIR

ver. 1.02 < 0.2 pixels

< 0.2 pixels < 0.5 pixels

< 15 m < 50 m

ver. 2.0 < 0.1 pixels

< 0.2 pixels < 0.2 pixels

< 15 m < 50 m

SNRs Measured in Actual Data

212> 549

213> 708

177> 547

181> 546

177> 545 Onboard lamp data

(the minimum values for Lamp-A, higher than the specified input radiance)

218> 1404

SWIR

136> 1403N

200> 1402

Onboard lamp data

(slightly lower than the specified input radiance)

224> 1401

VNIR

RemarksMeasured

Value

Specified

Value

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 1.0 2.0 0.75 0.12 – 0.18

1 2 56789430.1

1

10

100

0.4 0.8 1.2 1.6 2Rad

ianc

e(mW cm-2

micrometer-1

ster-1)

Wavelength (micrometer)2.4

200

300

400

500

6008001000

Detection ofHigh TemperatureTargets

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 missionanalysis

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 ofASTER 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

1. Data Acquisition Based Upon User’s Requests2. Instrument Operation Constraints

(1) Data Rate・ Maximum average data rate : 8.3 Mbps・ Peak data rate : 89.2 Mbps

(2) Power Consumption(3) Pointing Change

3. Selection of Operation Mode / Gain Settings4. Utilization of Cloud Prediction Data

Automatic Generation of Data Acquisition Schedule

Duty Cycle : 8%

ASTER US-JAPAN RelationASTER US-JAPAN RelationASTER US-JAPAN RelationASTER US-JAPAN Relation

Pacific Link

TDRS

ASTER GDS

TDRSSUSJapan

EOSDIS

data

DRS

Direct Downlink

・ Data Processing/Analysis (Level 0→Level 1) (High Level Product) ・ Mission Operation (Observation Scheduling)・ Data Archive/Delivery

User

ATLASⅡ

User

Terra ASTER Sensor

Product ProductDAR, DPR DAR, DPR

Activity

Telemetry dataExpedited Data Set

Science dataEngineering dataTelemetry data

Command

DownlinkUplink

Product

Level-0 data

ASTER Standard Data Products

Category #Product name Generation

Japan US

Max scenes

in Japan

Standard

1A Reconstructed, unprocessed instrument data ○ × 780

1B Radinace at sensor ○ × 310

2A01 Brightness temperature at sensor × ○ －

2A02 Relative spectral emissivity (D-stretch) ○ ○ 50

2A03 Relative spectral reflectance (D-stretch) ○ ○ 50

2B01 Surface radiance ○ ○ 10

2B03 Surface temperature ○ ○ 10

2B04 Surface emissivity ○ ○ 10

2B05 Surface reflectance ○ ○ 10

4A Polar cloud map (after launch) × ○ －

4A21 Digital elevation model (Absolute) × ○ －

Semi-

standard

3A01 Radinace at sensor with orth-photo coreetion ○ × 30

4A01 Digital elevation model (Relative) ○ × 30

ASTER Primary ObjectivesASTER Primary Objectives

To improve understanding of the local- and regional-scale processes occurring on or near the earth’s surface.

Obtain high spatial resolution image data in the visible through the thermal infrared regions.

ASTER is the zoom lens of Terra!

ASTER Web Site:http://asterweb.jpl.nasa.gov

APPLICATIONSAPPLICATIONS• Surface Energy Balance• Geology • Wild Fires• Urban Monitoring• Glacial Monitoring• Volcano Monitoring• Wetland Studies• Land Use

Surface Energy Surface Energy BalanceBalance

Surface Energy Balance from ASTER dataEl Reno OK, 4-Sep-2000, Kustas & Norman 2-source model

ASTER data of El Reno OK, 4-Sep-2000: NDVI & Surface Temperature

GeologyGeology

3 2 1 3 2 1 DST

4 6 8 DST 13 12 10 DST

Wild FiresWild Fires

Hayman Fire, Hayman Fire, ColoradoColorado

June 16, 2002 June 16, 2002

ASTER bands 8-3-2 ASTER bands 8-3-2 as RGBas RGB

Urban MonitoringUrban Monitoring

Eiffel Tower

Louvre

Arc de Triomphe

La Defense

Glacial MonitoringGlacial Monitoring

Global Land Ice Measurements from SpaceGlobal Land Ice Measurements from Space

View from top of Llewellyn Glacier, British Columbia

Goal is to determine the extent of world’s 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 MonitoringVolcano Monitoring

Nyiragongo erupted January 17, 2002 sending streams of lave Nyiragongo erupted January 17, 2002 sending streams of lave through the town of Goma. More than 100 people were killed. through the town of Goma. More than 100 people were killed. This perspective view combines ASTER thermal data (red) This perspective view combines ASTER thermal data (red) showing the active lava flows and lava in the crater; Landsat showing the active lava flows and lava in the crater; Landsat Thematic Mapper image, and Shuttle Radar Topography Thematic Mapper image, and Shuttle Radar Topography Mission digital elevation data.Mission digital elevation data.

January 2002 Eruption of Nyiragongo Volcano, CongoJanuary 2002 Eruption of Nyiragongo Volcano, Congo

Wetland StudiesWetland Studies

Sediment Image Temperature Image

Land UseLand Use

US-Mexico border at Mexicali

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: http://harp.gsfc.nasa.gov/~imswww/pub/imswelcome/

• Submit a Data Acquisition Request: First become an authorized user; then request satellite obtain your particular data