04 July 2022
29 June 2020
The start of satellite remote sensing
The first Earth-orbiting satellites were launched in the 1950s. These satellites were thought to improve our understanding of the Earth’s magnetic field, and resulted in the discoveries such as the Van Allen belts from NASA’s Explorer-1 satellite observations. Very quickly, the attention turned to launching satellites capable of assisting weather forecasting on a regular basis. Since the 1960s, these weather satellites collected data in forms and media that were, at the time, at the forefront of technology. As weather satellites got better and better, collecting higher resolution data that were more accurate, the old satellite data became less interesting for researchers. Today, however, it is recognised that early satellite observations, even if there are of inferior quality, help to better understand environmental changes since the 1960s.
A unique legacy
Although these early satellite missions did not go without trouble, they have left a unique legacy. They observed and recorded the exact environmental situation on Earth at a given point in time. Exploiting this information in retrospect can enable to pinpoint the precise situation of our planet’s climate, for example to get a better picture on the extent of polar ice caps in the 1960s . In addition, with modern techniques, such as climate reanalysis , it is possible to piece together information collected by the first satellites. In such a case, the early information observed by these satellites is crucially important to generate digital datasets that span several decades .
Why is it important to rescue satellite data?
Data rescue is the process of preserving satellite data at risk of being lost due to loss or deterioration of the storage media or due to loss of experience or information on how to read these data. Data rescue is critically important for climate and reanalysis activities to ensure that scientists and users maintain access to satellite data all the way back to the beginning of operations. The priority of data rescue is preserving these original data so that they can remain usable by future generations. Besides rescuing the data, it is necessary to correct for geometric and radiometric effects, and to reformat the data to today’s digital standards. This is to allow for ingestion by standardized algorithms and software. For data users, this represents a major advancement as compared to the bespoke efforts that were required originally by investigators for analysing the data from each particular satellite instrument. Yet, exploiting the sheer volume of satellite data collected over several decades is another feat for Earth and data scientists to achieve.
What data are rescued today?
EUMETSAT’s first efforts to rescue satellite data for climate research started in the framework of two European Union Funded FP7 projects (ERA-CLIM and ERA-CLIM-2) that, among others, aimed at rescuing and reprocessing historic satellite data, such as data from the Meteosat Visible and Infrared Imager (MVIRI) on early Meteosat satellites. EUMETSAT gives special emphasis on data from the first Meteosat satellite that were not part of EUMETSAT’s archive until a copy of most of the data was found in the United States in 2015.
EUMETSAT supported the recovery of data collected by two infrared sounding Spectrometer Interferometer-1 (SI-1; Kempe et al. 1980) instruments flown on former Soviet meteorological polar-orbiting satellites (Meteor-28 and Meteor-29). Fortunately, the investigators who had worked on SI-1 in the late 1970s had preserved all (about 2000) original SI-1 spectra (between 6 and 25 µm). The data were quality controlled, georeferenced, and moved to a current data format (Coppens et al. 2015).
The work on rescuing data from heritage instruments, such as MFG and AVHRR, continued in association with the European Union Funded H2020 Fidelity and uncertainty in climate data records from Earth Observations (FIDUCEO) project, the Copernicus Climate Change Service (C3S) , and the European Space Agency (ESA) Long-Term Data Preservation Programme , which are examples of fruitful collaborations with international partners.
Further details can be found in the references including Poli et al. (2017) that provides an overview of recent advances in data rescue.
References
Coppens, D., B. Theodore, W. Doehler, A. Damiano, D. Oertel, D. Klaes, J. Schmetz, and D. Spaenkuch, 2015: Exploitation of SI-1 data fromMeteor 28 and 29 spacecraft for climate purposes. EUMETSAT Meteorological Satellite Conf., Toulouse, France, EUMETSAT. [Available online at https://cimss.ssec.wisc.edu/itwg/itsc/itsc20/program/PDFs/30Oct/session7b/7p_07_coppens.pdf ]
Kempe, V., D. Oertel, R. Schuster, H. Becker-Ross, and H. Jahn, 1980: Absolute IR-spectra from the measurement of Fourier-spectrometers aboard Meteor 25 and 28. Acta Astronaut, 7, 1403–1416, doi: https://doi.org/10.1016/0094‑5765(80)90015-6
Poli, Paul; Dick P. Dee; Roger Saunders; Viju O. John; Peter Rayer; Jörg Schulz; Kenneth Holmlund; Dorothee Coppens; Dieter Klaes; James E. Johnson Asghar E. Esfandiari; Irina V. Gerasimov; Emily B. Zamkoff; Atheer F. Al-Jazrawi; David Santek; Mirko Albani; Pascal Brunel; Karsten Fennig; Marc Schröder; Shinya Kobayashi; Dieter Oertel; Wolfgang Döhler; Dietrich Spänkuch; Stephan Bojinski, 2017: Recent Advances in Satellite Data Rescue, Bull. Amer. Meteor. Soc. (2017) 98 (7): 1471–1484. https://doi.org/10.1175/BAMS-D-15-00194.1