•Telescope and FPA’s
–aspheric off-axis optics
–33 cm unobscured  aperture
–5 Si:As detector arrays
•18.3 arc sec square pixels
•9.15” cross-scan sampling
•1° cross-scan fov
–3 - 26 µm interferometer
•6 detectors
•2 to 20 cm-1 resolution
•944 liter solid H2 dewar
–~ 10 months on-orbit lifetime
•4/24/96 launch - 2/26/97  EOL
The MSX IR Sensor
4
• Data Acquisition             - 0.05°/sec scan rate
-  5Mps data rate
The MSX Infrared sensor was built by the Space Dynamics Laboratory of the Utah State University.  This off-axis telescope had a 33 cm clear aperture and a 896 cm² collecting area.  The optics exceeded the design requirement to be diffraction limited at 12 μm to which the detectors were sized.  The focal plane radiometer sub-assembly contained five line-scanned infrared focal plane array.  The entire system was cooled by a 944 liter solid H2 cryostat.  The Si:As focal plane arrays had eight columns of detectors, each consisting of 192 rows of 18.3" square pixels. Half the columns were offset by half a pixel, providing critical sampling in the cross scan direction. To reduce the telemetry rate, only half the columns were active but at least one column was active on either side of the stagger.
The 4.3 µm spectral band was divided in cross-scan by two different near-infrared filters centered on the 4.3 μm atmospheric CO2 band. These near-infrared bands had isophotal wavelengths and bandwidths of λ = 4.29 µm, Δλ = 0.104 µm and λ = 4.25 µm, Δλ = 0.179 µm. The effective beam size for each bands was measured to be 140 µsr and the full width at half maximum response was about 23”.  Thus, the resolution was about 30” and the data were adequately sampled by the half detector cross-scan offset of the two columns that were active for this focal plane array and by the seven in-scan data samples per dwell time on a detector.  The filter mask in the center of the array limited the field of view of the individual sub-arrays to 0.4°.