Reviving historical IRS-P3 MOS data with adaptations to modern standards, requirements, and algorithms

Abstract

The Modular Optoelectronic Scanner (MOS) instrument was an experimental imaging spectrometer built by the German Aerospace Center (DLR) and launched in March 1996 aboard the Indian Remote Sensing Satellite P3 (IRS-P3) spacecraft. The mission was primarily dedicated to the study of ocean colour and atmosphere but also providing observations over land. It ended on May 31, 2004.

The instrument consisted of three independent spectrometers with a total of 18 channels in the visual and short-wave infrared range and a swath width of 200 kilometres. In addition to the sensor, DLR also developed the processor software and organized the mission operations. The mission was conducted in cooperation with the Indian Space Agency (ISRO), the European Space Agency (ESA), and the American National Aeronautics and Space Administration (NASA).

Considerable effort was put into ensuring the best data quality possible. An on-board solar diffuser allowed for an absolute radiometric calibration. Internal control lamps were available for long-term monitoring of the instrument and regular dark measurements were performed.

IRS-P3 MOS data constitute an important contribution to the CEOS Ocean Colour Radiometry Virtual Constellations. Its data narrow the temporal data gap between the Coastal Zone Color Scanner (CZCS) on Nimbus 7, which flew from 1978 - 1986 and SeaWiFS launched in September 1997. It also nicely complements the latter data in terms of spectral and spatial resolution.

The IRS-P3 MOS European Dataset Curation project under the ESA Heritage Space programme aims at consolidating MOS data in the DLR and ESA archives and to create a unified European master data set. The processors employed during mission's lifetime are being re-implemented and improved, integrating all correction algorithms developed at the time, such as stray light correction and destriping. The data will be reprocessed to level-1B and a new level-1C product, both in NetCDF, providing the basis for a possible future level-2 product. The products as well as the required calibration and reference data are processed into to a new product structure with a harmonized product format and file naming convention. The aim of the project is to provide high-quality data products for the user community.

This contribution discusses the advantages and challenges arising from the preparation and processing of historical satellite data in line with state-of-the-art standards and requirements.