SIRIS (Stratospheric InfraRed Interferometer Spectrometer)

SIRIS was the acronym for Stratospheric InfraRed Interferometer Spectrometer an emission-mode remote-sensing instrument developed at the NASA Goddard Space Flight Center during the 1980's decade for measurement of the earth-limb from a balloon platform. The instrument was built to further understanding of ozone behavior in the stratosphere and catalytic cycles which control the ozone concentration.

The instrument scheme can be seen at left (click to enlarge). A rotatable target mirror provided for measurements of the earth's limb, the earth's surface 45º down from the local horizon and calibration targets. The field of view was 0.5º. The spectrometer consisted of a commercial laboratory Michelson interferometer adapted for cryogenic temperatures with the interferometer and associated optics operating at ~112º K. During scanning, alignment of the interferometer fixed mirror was dynamically maintained through feedback signals driving alignment transducers on the fixed mirror. The alignment was monitored using a He-Ne laser beam through the center of the interferometer optics.

The interferometer output was directed to five Si:Ga photoconductor detectors inside a liquid Helium Dewar; one detector was for the wide band and the other four were for the narrow bands of the spectrum. The instrument was capable of operating from a balloon platform for periods up to 30 hours, thus allowing the concentrations of trace species to be monitored through a complete diurnal cycle. Use of the emission mode allowed observations at all times during the diurnal cycle and along a line of sight (LOS) of constant local time (either north or south). Remote sensing of the limb allowed vertical coverage from the middle troposphere to 40 km (the balloon altitude) with a vertical resolution of 3 km (1/2 scale height). Observations were taken at a series of tangent heights (the so-called limb sequence) and inverted to obtain gas concentration vs altitude.

Balloon launched on: 10/28/1983 at 23:49 utc
Launch site: Columbia Scientific Balloon Facility, Palestine, Texas, US  
Balloon launched by: National Scientific Balloon Facility (NSBF)
Balloon manufacturer/size/composition: Zero Pressure Balloon Winzen 3.100.000 cuft (Stratofilm) - SF198.17-120-NSH-02
Balloon serial number: W3.1-0-25
Flight identification number: 1355P
End of flight (L for landing time, W for last contact, otherwise termination time): 10/29/1983 at 12:16 utc
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): 13 h 50 m
Landing site: 25 miles ENE of Bugalusa, Louisiana, US
Payload weight: 1847 lbs

• Cryogenic Fourier spectrometer for measuring trace species in the lower stratosphere Applied Optics Vol. 27, Issue 23, pp. 4964-4976 (1988)