An experimental reflector allows the calibration of the Sentinel-6 satellite’s altimeter from the Montsec Observatory
The isardSAT enterprise has designed and installed at the Montsec Observatory, managed by the IEEC, a reflector to calibrate the altimeter.
This device has demonstrated exceptional performance, comparable to that of more complex and expensive devices used by institutions such as ESA or NASA.
Since its launch in 2020 as part of the European Commission's Copernicus programme, the Sentinel-6 satellite has been analysing key variables such as sea level rise caused by climate change using the Poseidon-4 altimeter. isardSAT, an R&D company that offers services and solutions in the field of satellite Earth observation, has developed a reflector capable of calibrating the altimeter with high precision (around one centimetre), and thanks to a much less costly and complex technology than that commonly used.
The reflector has been installed at the Montsec Observatory (OdM), an infrastructure managed by the Institute of Space Studies of Catalonia (IEEC). This site, located at an altitude of 1,570 metres in the Montsec mountain range, is recognised as one of the best in Europe for astronomical observation, thanks to the combination of good weather conditions and low light pollution, which provide exceptional night sky conditions.
Poseidon-4, the radar altimeter on board the Sentinel-6 satellite, continuously measures the distance between the satellite and the Earth's surface. Its data are used both for short-term weather forecasts and for global oceanographic and climate studies. Like any advanced data processing, this instrument needs periodic calibration to verify that it is working properly, a process that is accomplished by placing devices on Earth at known locations with specific characteristics.
Calibration of altimeters is usually done with transponders, which are complex and expensive active equipment available only to large institutions such as ESA or NASA. But recent advances in signal processing algorithms have made it possible to calibrate altimeters using less complex and more affordable instrumentation: passive reflectors. Unlike transponders, these devices reflect satellite waves without the intervention of any electronic device; they use only three orthogonally positioned metal plates.
Location of the Montsec Observatory with respect to the Sentinel-6 track.
Credit: isardSAT (from Google Earth)
In order to test the potential of this technology with the Sentinel-6 altimeter, isardSAT has developed and installed a reflector at the Montsec Observatory. This site, in the municipality of Sant Esteve de la Sarga (Pallars Jussà), has many advantages for the operation of the reflector, such as its proximity to the Sentinel-6 track, the fact that it is a prominent location (in height) and far from the possible interferences caused by urban centres, and the presence of a meteorological station that offers a large amount of data needed for the calculation of small additional geophysical corrections. On the other hand, the fact that it is located inside the enclosed area of the observatory facilitates maintenance tasks by IEEC technical staff.
Since the installation and adjustment of the reflector in September 2021, the data acquired by the Poseidon-4 altimeter of Sentinel-6 as it passes over the Montsec Observatory show exceptional accuracy, measuring the distance between the satellite and the Earth (more than 1,300 km away) with a margin of error of a few centimetres and an accuracy of about one centimetre. These results, comparable to those obtained by transponders, are essential for the rest of the satellite's measurements around the Earth, and have already been presented at several international conferences.
The isardSAT team installed the reflector at the Montsec Observatory (OdM – IEEC) in April 2021.
Credit: isardSAT
Press release prepared in collaboration with the Communication Office of isardSAT.
Main Image
Image caption: Image of the reflector, with the Joan Oró Telescope building behind it, inside the facilities of the Montsec Observatory (OdM – IEEC).
Credit: IEEC
More information
The Institute of Space Studies of Catalonia (IEEC — Institut d’Estudis Espacials de Catalunya) promotes and coordinates space research and technology development in Catalonia for the benefit of society. IEEC fosters collaborations both locally and worldwide and is an efficient agent of knowledge, innovation and technology transfer. As a result of 25 years of high-quality research, done in collaboration with major international organisations, IEEC ranks among the best international research centres, focusing on areas such as: astrophysics, cosmology, planetary science, and Earth Observation. IEEC’s engineering division develops instrumentation for ground- and space-based projects, and has extensive experience in working with private or public organisations from the aerospace and other innovation sectors.
IEEC is a private non-profit foundation, governed by a Board of Trustees composed of Generalitat de Catalunya and four other institutions that each have a research unit, which together constitute the core of IEEC R&D activity: the Universitat de Barcelona (UB) with the research unit ICCUB — Institute of Cosmos Sciences; the Universitat Autònoma de Barcelona (UAB) with the research unit CERES — Center of Space Studies and Research; the Universitat Politècnica de Catalunya · BarcelonaTech (UPC) with the research unit CTE — Research Group in Space Sciences and Technologies; the Spanish Research Council (CSIC) with the research unit ICE — Institute of Space Sciences. The IEEC is a CERCA (Centres de Recerca de Catalunya) centre.
Contacts
IEEC Communication Office
Barcelona, Spain
E-mail: comunicacio@ieec.cat
isardSAT Communication Office
Barcelona, Spain
Lluís Bassa Tomàs
isardSAT
E-mail: Lluis.Bassa@isardSAT.cat