2 research outputs found
A New Orbiting Deployable System for Small Satellite Observations for Ecology and Earth Observation
In this paper, we present several study cases focused on marine, oceanographic, and
atmospheric environments, which would greatly benefit from the use of a deployable system for
small satellite observations. As opposed to the large standard ones, small satellites have become an
effective and affordable alternative access to space, owing to their lower costs, innovative design
and technology, and higher revisiting times, when launched in a constellation configuration. One
of the biggest challenges is created by the small satellite instrumentation working in the visible
(VIS), infrared (IR), and microwave (MW) spectral ranges, for which the resolution of the acquired
data depends on the physical dimension of the telescope and the antenna collecting the signal. In
this respect, a deployable payload, fitting the limited size and mass imposed by the small satellite
architecture, once unfolded in space, can reach performances similar to those of larger satellites.
In this study, we show how ecology and Earth Observations can benefit from data acquired by
small satellites, and how they can be further improved thanks to deployable payloads. We focus on
DORA—Deployable Optics for Remote sensing Applications—in the VIS to TIR spectral range, and
on a planned application in the MW spectral range, and we carry out a radiometric analysis to verify
its performances for Earth Observation studies
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Analysis of Gnss-R Observations for Altimetry and Characterization of Earth Surfaces
Global Navigation Satellite Systems (GNSS) provide abundant, opportunistic signals that can be used to probe the Earth’s environment and surface. Utilizing reflected GNSS signals for remote sensing is called GNSS Reflectometry (GNSS-R). Sensing of the ocean, land, and ice, with potentially dense measurement coverage and rapid revisit times, is possible due to the distributed geometry of GNSS constellations. GNSS-R can provide some advantages over other Earth observation systems, like traditional radar altimeters or microwave radiometers. GNSS signals are well characterized and encoded with precise ranging and timing information. There are multiple transmitters in view at any time, and GNSS signals occupy a protected frequency band (L-band) that penetrates Earth’s atmosphere in all weather conditions.This dissertation focuses on the development of methods and analysis techniques to observe sea surface height and sea ice extent with reflected GNSS signals. A tool-kit is developed to take advantage of experimental data sets from aircraft and spacecraft, and to produce state-of-the-art altimetric retrievals. Algorithms for the re-tracking of altimetric delays are demonstrated. Techniques to characterize and models to correct GNSS-R path delay errors are built through analysis of TechDemoSat-1 (TDS-1) and NASA’s Cyclone Global Navigation Satellite System (CYGNSS) flight data. Neither TDS-1 nor CYGNSS were designed to make precise altimetry observations. Thus, this work evaluates practical performance limitations of these GNSS-R observations, and establishes requirements for future missions. Altimetry results with height retrieval standard deviation of σH = 11 m with 1 sec and σH = 3.8 m with 10 sec observations, are shown.This work creates a foundation of techniques that can support future GNSS-R missions dedicated to ocean surface altimetry by producing results with sufficient accuracy and precision to the ocean science community. These tools are built to inform future mission designs and aid scientific interpretation of GNSS-R measurements