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ACD Airborne FTS Spectrometer. History Acquired in 1974 for measurements of stratospheric composition Flown 800-1000 hours on NCAR Sabreliner Flown 800-1000 hours on NASA DC-8 Also flown on Electra, P-3 Extensively modified in 1999. ACD Airborne FTS Spectrometer. Specifications
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ACD Airborne FTS Spectrometer • History • Acquired in 1974 for measurements of stratospheric composition • Flown 800-1000 hours on NCAR Sabreliner • Flown 800-1000 hours on NASA DC-8 • Also flown on Electra, P-3 • Extensively modified in 1999
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 1.6-20 mm (KBrbeamsplitter) • Dual detectors • InSb 2.5-6 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
ACD Airborne FTS Spectrometer • Normal operation • Observe sun near sunset (or sunrise) • Photoguidedautogain solar tracker (~10”) • Average about 1 min. observations • Bandpass filter • SNR a few hundred (detector dependent) • Usually in shot noise regime
Challenges • Low signals • Observing time • Guiding • Windows and observing port Will probably be operating in background noise limited regime