65 Environmental observation Arguably, the most important use for new satellites is to perform cost-effective surveys of the Earth, given the planetwide data they can deliver. As a result, NASA’s Jet Propulsion Laboratory (JPL) has several CubeSat missions now in orbit, gathering data on a range of environmental parameters. The Geo-Cape ROIC In-Flight Performance Experiment (Grifex) for instance is a 3U CubeSat launched in 2015 to perform engineering assessments of a JPLdeveloped all-digital in-pixel, high frame rate, read-out integrated circuit (ROIC) with a frame rate of 16 kHz. The core aims of the mission are to verify with real-world testing the performance, functionality and data integrity of the ROIC in space for use in instruments and missions revolving around imaging interferometry. The missions include geostationary coastal and air pollution event (Geo-Cape) surveys, and high spectra resolution studies and measurements of atmospheric compositions, from geostationary Earth orbit (GEO) or other altitudes. Grifex has also integrated the Geo-Cape PanFTS (Panchromatic Fourier Transform Spectrometer), an imaging instrument designed to operate from GEO, with the CubeSat serving to demonstrate the PanFTS’ digital focal plane assembly and signal chain technology. The PanFTS can measure a range of trace gases at high resolution, being sensitive in the UV, visible and IR wavelengths. It covers a spectral range of 260 to 3500 nm with a ground resolution of 4 x 4 km, and has a repeat cycle of 1 to 2 hours. As a result, its technology could support chemical transportation modelling, pollutant monitoring and assessing the amounts of ozone and aerosols among others in the Earth’s atmosphere. With the study of such environmental parameters becoming imperative for most of the world’s governments, NASA’s international SWOT (Surface Water and Ocean Topography) satellite has in recent months been increasingly deployed for its orbital oceanographic data, NASA reported in September this year. SWOT was developed for measuring the heights of every body of water on Earth. Following the 2023 summer however, its survey data has been used to better understand El Nino, the periodic climate phenomenon that disrupts the Earth’s weather. Given that water expands when warmed, El Nino tends to be characterised by higher than average sea levels as well as warmer than typical ocean temperatures, particularly along the US West Coast. The spacecraft’s capability is achieved through the KaRIn (Ka-band Radar Interferometer) instrument, which uses two antennas spread 33 ft (10 m) apart on a boom to produce a pair of data swathes as it orbits the Earth to collect waterheight measurements by bouncing radar pulses off the water’s surface. Space vehicles | Insight Arguably, the most important use for new satellites is to perform costeffective surveys of the Earth, given the planet-wide data they can deliver Uncrewed Systems Technology | October/November 2023 The Surface Water and Ocean Topography spacecraft is key to the present forecasting for El Nino (Courtesy of NASA JPL)
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