FIGOSat: First Interoceanic GNSS-reflection Observation Satellite
- Paper number
IAC-05-B5.4.07
- Author
Ms. Sioe Wen Go, The Netherlands
- Year
2005
- Abstract
FIGOSat: First Interoceanic GNSS-reflection Observation Satellite
To make a competitive mini-satellite, with a passive system using sea surface GNSS reflections for altimetry
In 1978 the first satellite with altimeter was launched, this satellite (Seasat) demonstrated that radar altimeters could measure its own height above the sea surface to a precision of about 10 cm. Since then various missions have flown altimeters with increasing accuracy that revolutionized the gathering of knowledge of the ocean. Events such as El Niño, the complex pattern of sea level anomalies and western boundary currents can now be investigated using altimetry. The conventional technique uses active radar to measure the sea level height. A new technique to measure sea level height is by making use of signals of opportunity. These signals of opportunity can originate from different GNSS-systems, like GPS, GLONASS and future Galileo. These signals of opportunities are a big advantage for satellites that observe the ocean, because no active radar is needed. Because this is a rather new technique, it still needs a lot of research before it can become operational. One of the questions that need to be addressed is if it is possible to create a satellite system to measure sea level height by using GNSS-reflections that can compete with conventional altimetry satellites. The FIGOSat mission consists of two innovative parts. The use of GNSS-reflections is the first.
The second innovative part of this mission is the use of a phased array antenna. A phased array antenna is build of a number of small elements that can receive and send signals like a conventional antenna dish. The phased array has some advantages. The first is that a phased array can steer a beam electronically and the second is that it can produce more beams simultaneous. This antenna is chosen to make fully use of the opportunity of the GNSS-reflections. With this antenna it is possible to see a much wider area, up to 80 degrees, to scan for the reflections points and up to 12 points can be measured simultaneously.
So the FIGOSat mission has two innovative features. Making it possible to use signals of opportunity, the GNSS-reflection signals, for altimetry and the second feature is the use of a phased array antenna to do this. The feasibility study makes it clear that this is possible and that we can use these features to make a competitive system. The use GNSS-reflections are feasible when the antenna is designed for a gain to receive the weak signal. A phased array antenna is the best solution to do this. The antenna has a big Field of View, because it can steer the beam, and can receive up to 12 specular points simultaneous. The total satellite will be of low mass. So it will be a mini satellite that is easy to handle and cheap to launch. But there is still a lot of development necessary especially on the payload and the software. The prototype of the payload has less gain, doesn’t have a receiver and antenna suitable for space and has a viewing angle of only 30 degrees. The development is the main reason of the cost budget overrun. When the development cost can be split with other mission that want to use such a phased array antenna, then the mission will become cheap. The next step is to design and test the satellite.
Current altimeter missions will come to an end and then a successive mission is necessary to keep on gathering data. This successive altimeter mission could be the FIGOSat mission.- Abstract document
- Manuscript document
IAC-05-B5.4.07.pdf (🔒 authorized access only).
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