SCISAT 1 is a Canadian (CSA) atmospheric research satellite that was launched at 02:10 UT by a Pegasus XL rocket released from an L-1011 cargo plane flying out of Vandenberg AFB on 2003 August 13. The 152-kg, 70-W, "bias momentum stabilized" spacecraft points to the Sun at one degree accuracy, and carries two instruments, FTS and MAESTRO, to monitor the atmospheric ozone and dust composition in the 4-100 km altitude range. The initial orbital parameters were period 97.7 min, apogee 655 km, perigee 642 km, and inclination 73.9 deg.
FTS (Fourier Transform Spectrometer) is basically a Michelson interferometer telescope with a primary lens, three secondary lenses at either side of a narrow slit, a beam splitter, a fixed mirror at the end of one beam and a movable mirror at the end of the other. The reflected beams recombine after re-entering the splitter, providing reinforced, annihilated or partially combined intensities, as the movable mirror is tuned. At an absorption band, in this case corresponding to a ozone absorption band, even the reinforced intensity will be weak. The telescope is pointed at the setting or rising Sun so that the long horizontal path in the atmosphere maximizes the absorption at the (ozone) bands of interest. During the progression of the Sunrise/set, the data contains decipherable information on the vertical distribution of the ozone molecule. A Fourier transform is performed on the detector output, to decontaminate the output, so that the intensities are purely at discrete wavelengths, uncontaminated by partial contributions from nearby wavelengths.
MAESTRO (Measurements of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation) is a reflecting grating telescopic spectrometer consisting of a primary lens, a slit flanked by secondary lenses on either side, a plane reflecting grating and a detector. By slowly rotating the grating, lights of different wavelengths will be enabled to impinge on the photoelectric detector. In addition to providing a spectrum of sunlight at the rising and setting positions, it will also enable derivation of the atmospheric extinction due to aerosols and dust. No Fourier transformation of the detector output is called for.
Alternate Names
ACE
Atmospheric Chemistry Experiment (ACE)
Facts in Brief
Launch Date: 2003-08-13
Launch Vehicle: Pegasus XL
Launch Site: Vandenberg AFB, United States