ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station
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The ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) will be implemented by placing the existing space-ready Prototype HyspIRI Thermal Infrared Radiometer (PHyTIR) on the International Space Station (ISS) and using it to gather the measurements needed to address the science goals and objectives. PHyTIR was developed under the Earth Science Technology Office (ESTO) Instrument Incubator Program (IIP). From the ISS, PHyTIR will provide data with 38-m in-track by 69-m cross-track spatial resolution (science requirement is 100 m) and predicted temperature sensitivity of ≤0.1 K (science requirement is 0.3 K). The ISS orbit allows excellent coverage of the selected targets including diurnal coverage. The existing hardware was developed to reduce the cost and risk for the thermal infrared radiometer on the future Hyperspectral Infrared Imager (HyspIRI) mission, A double-sided scan mirror, rotating at a constant 25.4 rpm, allows the telescope to view a 53°-wide nadir cross-track swath as well as two internal blackbody calibration targets every 1.29 seconds (Note that the two-sided mirror rotating at 25.4 rpm provides 46.6 sweeps per minute). The optical signal is focused by a telescope onto the 65 K focal plane containing a custom 13.2-μm-cutoff mercury-cadmium-telluride (MCT) infrared detector array. Spectral filters on the focal plane define 5 spectral bands in the 8-12.5 μm range and an additional band at 1.6 um for geolocation and cloud detection (six bands total). The focal plane is cooled by two commercial Thales cryocoolers. Electronics consist of six build-to-print and four commercial boards. Heat rejection for the ECOSTRESS cryocoolers and electronics is provided by the cooling fluid loop on the ISS Japanese Experiment Module External Facility (JEM-EF). ECOSTRESS can fit any of the nine JEM-EF payload locations but will be deployed at Site 10 (one of the two end locations).

Table 2. ECOSTRESS Radiometer Characteristics

scan angle

DescriptionValueUnitNotes
Number of spectral bands 6  
Measured band centers Band 1 - 8.29, Band 2 - 8.78, Band 3 - 9.20, Band 4 - 10.49, Band 5 - 12.09 µm  
Measured FWHM per band Band 1 - 0.354, Band 2 - 0.310, Band 3 - 0.396, Band 4 - 0.410, Band 5 - 0.611 µm
Pixel size at nadir 69x38 m 2 pixels in cross track and 1 pixel in down track
Swath width 384 km varies with ISS height, assumes height of 400 km
Nominal Radiometric accuracy at 300K 0.5 K typical value varies with wavelength of band
Nominal Radiometric precision at 300K 0.15 K typical value varies with wavelength of band
Radiometric precision at 300K per band 0.21,0.13,0.10,0.10,0.29 K measured values (TVAC)
Number of blackbodies 2 One controlled between 16C to 24C, One controlled to 46C
Hot blackbody temperature 46 C The scanning sequence is hot bb, cold bb, earth scene repeating
Cold blackbody temperature 20 C The scanning sequence is hot bb, cold bb, earth scene repeating
Dynamic range 200-435 K varies with spectral band, 12um band saturates at the highest temperature (excluding the SWIR)
Aperture size 200 mm  
F-number 2.1    
Detector readout rate <10 MHz per channel, 32 total channels
Scan speed 25.4 rpm  
Scan angle +/- 25 degrees
Detector Array size 10.24 mm2 Sparse array
Downlink rate 4.5 Mbps Transmission rate is fixed at 10 Mbps (firmware limitation)
Scene size 44 swaths 9.8km x 384km =3D 1 swath
Number of scenes 16   assuming one per orbit
Focal plane temperature 65 K  
Housing temperature 120 K  
Number of cyrocoolers 3   Pulse tube, < 500W
IFOV 96 µrads
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