A helium balloon lifted a set of terahertz sensors, developed in a TU Delft lab, to the edge of space on New Year’s Eve. These are the cameras for the Gusto mission that will map material in between stars.
Cases with all parts for the Gusto satellite arrived on Antarctica on 28 Octobre 2023. It would take another two months before Gusto could finally be launched on New Year’s Eve. (Photo: NASA/Scott Battaion)
“It was a tight schedule,” says Dr Jian-Rong Gao about the assembling and testing of the balloon satellite. Gao is the project leader for the Dutch contribution to the Gusto observatory – a satellite hanging from a helium balloon. It will map the distribution and composition of dust and gases between stars in the middle of the Milky Way, where stars are born and explode. Scientists hope this will help them understand more about stellar evolution.
Gao is an associate professor at the TU Delft Department of Imaging Physics (Faculty of Applied Sciences) and a senior instrument scientist at SRON (Netherlands Institute for Space Research). After a NASA competition, Gao was given the assignment to produce the on-board terahertz sensors six years ago. These are the ‘eyes’ of the Gusto (Galactic/Extragalactic ULDB Spectroscopic Terahertz Observatory) mission.
That was the starting point for the production of one eight pixel terahertz camera and the components for two more (see photos below). In total, TU Delft and SRON have invested 15 human years in their development, in addition to the R&D work by many master and PhD students before the Gusto project started.
Following closely
Gao followed the preparations for the launch as much as he could from his holiday address in Shanghai. Luckily he was in WhatsApp contact with team member Dr José Silva, who is his former PhD student and a SRON instrument scientist.
The equipment for the Gusto observatory arrived at the McMurdo balloon launch base on Antarctica’s Ross Ice Shelf on 28 October after a week’s delay. After it was assembled and tested, the launch depended on a favourable weather window.
This occurred on the last day of 2023. At 5:30 a.m. (Dutch time) on 31 December 2023, the giant helium balloon gently lifted Gusto to an altitude of 36 kilometres. At this time of year (December to February) the upper airstream forms a polar vortex, which will take the balloon with the observatory in a slow spin above and around the South Pole for about two months. After that, the balloon will eventually descend and end up either in the ocean or in Australia.
Terahertz waves, also called ‘submillimetre radiation’ or ‘terrifying high frequencies’, are somewhere in between infrared light and microwaves in the electromagnetic spectrum. Terahertz radiation is strongly absorbed by the gases of the atmosphere, therefore a terahertz observatory needs to be above the atmosphere. Conversely, gaseous elements like nitrogen or oxygen emit radiation in the terahertz range. The gusto satellite will map the sources of three frequencies (1.4, 1.9 and 4.7 THz) corresponding to the elements nitrogen, carbon and oxygen.
The inner Milky Way
During the approximately 55 days of observation time, Gusto will map the interior of our Milky Way looking for signs of nitrogen, carbon and oxygen in the clouds and the dust between the stars.
The Principal Investigator, Professor Christopher Walker (University of Arizona), proposed this type of mission back in 2014 as he expected that the distribution of heavier elements such as nitrogen, carbon and oxygen would tell him more about the birth and death of stars, and their evolution. He and his team will collect as much information as they can on the composition and distribution of the interstellar matter.
When Delta called Dr Gao on 7 January, Gusto was in operation. “Yesterday I heard that all the detectors are working well, but Gusto has not yet seen any Spectral lines . The team is now working on this. It may have to do with the direction in which the telescope is pointed. There might be an anomaly there.”
Gao doesn’t want to push Silva for updates. “It’s challenging. It’s a stressful thing. So it’s better to just let him tell me about the progress instead of me nagging him all the time.”
Use < and > to scroll – TU Delft’s Imaging Physics lab has produced there sets of eight terahertz sensors that record both intensity of the terahertz signal and its exact frequency. The oxygen camera has been built from eight sensors (pixels) and a beam splitter at SRON. The other two cameras have been assembled by NASA.
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