6. ACD Airborne FTS Spectrometer
History
Acquired in 1974 for measurements of stratospheric composition
Flown hours on NCAR Sabreliner
Flown hours on NASA DC-8
Also flown on Electra, P-3
Extensively modified in 1999

7. ACD Airborne FTS Spectrometer
Specifications
Aperture 5 cm, Cube corner reflectors
Scan length 16 cm OPD (~0.05 cm-1 resolution)
Scan time (normal) 6 sec
Range mm (KBr beamsplitter)
Dual detectors
InSb mm
HgCdTe 6-13 mm
Multiple bandpass filters, field stops
16 bit A/D with gain switching (19 bit dynamic range)
2 phase HeNe laser OPD reference
Air bearing moving mirror support

8. ACD Airborne FTS Spectrometer
Normal operation
Observe sun near sunset (or sunrise)
Photoguided autogain solar tracker (~10”)
Average about 1 min. observations
Bandpass filter
SNR a few hundred (detector dependent)
Usually in shot noise regime

9. Challenges Low signals Observing time Guiding
Windows and observing port
Will probably be operating in background noise limited regime