66 Insight | Space vehicles Ben Hamlington, a sea level researcher at JPL, comments, “SWOT’s ability to measure sea surface close to the coast will be invaluable for researchers but also forecasters looking at things like the development and progress of worldwide phenomena like El Nino.” Through this orbital data, and in combination with other sources, the US government’s National Oceanic and Atmospheric Administration has forecast a higher than 70% chance of a strong El Nino in winter this year, leading to a range of impacts on the weather and environment. SWOT was launched in December 2022 as a collaboration between NASA and the French space agency, CNES (Centre National d’Etudes Spatiales), with contributions from the Canadian and UK space agencies. A few months ago, NASA reported that a device called the Tropospheric Monitoring Instrument (Tropomi) has been used to explore how red solar-induced fluorescence (SIF) measurements could be used to detect Karenia brevis, a harmful red algae we discussed in issue 42 (February/March 2022) for researchers using UUVs in lakes to study factors influencing its growth and spread. Tropomi has the capacity to measure fine wavelengths of light: it is designed for a typical pixel size (near nadir) of 7 x 3.5 km2 for all spectral bands, except in the ultraviolet 1 band, where it is 7 x 28 km2, and SWIR bands where it is 7 x 7 km2. That ability could help agencies and communities better forecast and manage harmful outbreaks of the algae. The system is a payload co-funded by the ESA (European Space Agency) and the Dutch government’s Ministry of Economic Affairs and Climate Policy, Ministry of Education, Culture and Science, and the Ministry of Infrastructure and Water Management. It is deployed on the ESA’s Sentinel-5P satellite, and is designed principally as a spectrometer for sensing UV, visible, NIR and SWIR; these enable it to monitor ozone, methane, formaldehyde, aerosol, carbon monoxide, NO2 and SO2 in the atmosphere. The Sentinel-5P was launched in 2017 as part of the ESA’s Copernicus programme of uncrewed environmental monitoring spacecraft. It measures 1.40 x 0.65 x 0.75 m, carries 156 Ah worth of batteries and consumes 1.5 kW in standard operation. Orbital navigation Asked to name the various technologies on spacecraft, people often think first of the rocket engines, solar panels and radio equipment, but the navigation systems aboard satellites and launchers are also mission-critical and highly complex devices that require meticulous engineering and qualification for use in space – failures in them can almost never be addressed hands-on by repair technicians. Compared with terrestrial applications, inertial sensors made for space vehicles must be engineered with three unique considerations in mind. The first are the effects of operating in a vacuum, while the second is that the solutions must provide 8 to 15 years of uninterrupted use without servicing. Lastly, any cosmic radiation – varying as it does between different levels of orbit – must have no impact on the precision, accuracy or integrity of the sensors. “If you fail to account for those three problems, you could lose the gyro,” says Elliott de Toldi, product manager for inertial systems in space applications at Exail. “Lose the gyro and you will lose the mission, because without stability, satellites can’t observe, transmit or receive effectively, and launchers can’t maintain course.” Exail, through one of its two former companies iXblue, has been designing and producing space-qualified navigation solutions in partnership with Airbus Defence & Space for the past 20 years. October/November 2023 | Uncrewed Systems Technology Exail’s Astrix NS (New Space) is a FOG aimed at newer spacecraft such as SmallSats (Courtesy of Exail)
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