Initial in-orbit results from a low-cost atmospheric ozone monitor operating on board the FASat-Bravo microsatellite

Abstract

In 1994, a collaborative programme was set up between the University of Surrey and the Chilean Air Force to design and build a low-cost 50 kg microsatellite with instrumentation capable of monitoring the distribution and concentration of stratospheric ozone, particularly over Chilean territory. This resulted in the joint design and development of the ozone-layer monitoring experiment (OLME), which was flown on board the resultant FASat-Bravo microsatellite, launched in July 1998 into an 820 km altitude Sun-synchronous orbit. The nadir-pointing OLME measures the solar ultraviolet light backscattered from the atmosphere in four spectral bands. From these raw radiometric data, total column ozone concentrations can be deduced. Since the launch, a series of high-spatial-resolution measurements have been made over Chilean scientific stations, while continuous low-spatial-resolution measurements have been used to provide global coverage. To date, the University of Surrey has concentrated on these global measurements, and has used a simplified ozone retrieval algorithm to check the results qualitatively against ozone maps produced by NASA's Earth Probe Total Ozone Mapping Spectrometer (TOMS) payload. These initial results look promising, with apparently good correlation between the two datasets. A novel, more-complex retrieval algorithm has been applied to the high-resolution data, and early results have shown agreement with the TOMS.

Modern Small Satellites-Changing the Economics of Space

“…In particular, a series of microsatellites demonstrated steadily improved Earth observation capabilities from KITSat and PoSAT in 1994/5 (1km GSD 5 NIR) to ThaiPhutt the first multi-spectral imaging microsatellite to achieve 300m GSD (NIR, red, green, blue) -nevertheless, whilst interesting and educational, the image resolution and fidelity had no real commercial value. An example of useful science, however, came from the Chilean FASat-Bravo microsatellite (1998) that carried an instrument to monitor the distribution of ozone comprising two nadir-pointing UV cameras, one operating with CCD detectors, the other with UV photodiodes to derive relative global maps of total ozone concentrations that was calibrated against the NASA TOMS mission data [11]. FASat-Bravo also demonstrated an early use of the CAN-bus 6 on a microsatellite.…”

Low-cost microsatellite UV instrument suite for monitoring ozone and volcanic sulphur dioxide

“…The aim of this experiment was to study the ozone depletion in the Antarctic region with special attention to the Chilean territory. The project succeeded thanks to the collaboration between the Chilean Air Force and Surrey Satellite Technology Limited (SSTL) at the University of Surrey [5].…”

“…A silicon PIN detector is used for each channel, each with a sensitive area of 2.4 x 2.4 mm. The output photocurrent is digitised to 12-bit resolution and the instrument as a whole draws only 500 mW when in operation [5]. For this instrument a simple "quick-look" qualitative retrieval model for O 3 consisting of the negative logarithmic ratio of the 313 nm and 334 nm signals was developed.…”