SRON and TU Delft are on a mission for revelation of the process of star-evolution in greater detail with Dutch technology. NASA recently approved the budget for the balloon-borne telescope mission GUSTO which is led by University of Arizona. The GUSTO telescope will be equipped with three Dutch ‘cameras’ for three different ‘colours’ in the far infrared (FIR). The camera’s will measure emissions from the cosmic material between the stars called interstellar medium. SRON and TU Delft provide the key detectors and technology.
The data from GUSTO will provide the first complete study of all phases of the stellar life cycle. That cycle runs from the formation of molecular clouds, through star birth and evolution, to the formation of gas clouds and the re-initiation of the cycle. GUSTO stands for Galactic/Extragalactic ULDB Spectroscopic Terahertz Observatory. The observatory consists of a telescope of one meter in diameter, and three observation instruments carried by an Ultra-Long Duration Balloon (ULDB).
The balloon and telescope payload will fly on an altitude of 36 km above Antarctica, at the edge of space. SRON and TU Delft contribute so called hot electron bolometer multi-pixel (heterodyne) camera’s, operating at three Terahertz frequencies and also contribute a local oscillator unit and a novel phase grating that helps the detectors determine the exact colour of the far infrared light (FIR).
Untangle the complexities of the interstellar medium
GUSTO can detect carbon, oxygen and nitrogen emission lines. The unique and novel combination of data will provide information needed to untangle the complexities of the interstellar medium, and map out large sections of our Milky Way galaxy and the nearby galaxy known as the Large Magellanic Cloud.
The GUSTO mission is targeted for launch in December, 2021, from the station McMurdo on Antarctica, and is expected to stay in the air between 100 to 170 days, depending on weather conditions. Because of such a unprecedented long duration, GUSTO will use a super-pressure balloon where the volume of the balloon is kept relatively constant independent of the changes in the temperature of the contained lifting gas. This allows the balloon to keep a stable altitude for long periods. This is in contrast to a much more common variable-volume balloon only partially filled with lifting gas. The latter was used for GUSTO’s precursor STO2. STO2 was launched in 2016 as a pathfinder and flew for a duration of 23 days, demonstrating the Dutch key detector technologies from SRON and TU Delft.
Rotating with the Polar Vortex
The launch of GUSTO from Antarctica takes advantage of the Polar Vortex at an upper level low-pressure area, which rotates clockwise at the South Pole. Consequently, the balloon can ideally be returned. However, if the duration of the flight exceeds the period of the polar vortex, the telescope could fly beyond Antarctica and be lost in the end of mission like space telescopes are.
GUSTO will cost approximately $40 million in total. The Dutch part of the GUSTO project is largely financed by NASA, through University of Arizona. NASA supports 86% of the total costs in the Netherlands. SRON will work closely with the Kavli Institute of NanoScience at the TU Delft on the detectors and the phase gratings. The latter are a result of a PhD research of Behnam Mirzaei and are financially supported by the TU Delft Space Institute. SRON will build the 4.7 THz local oscillator using a so-called quantum cascade laser developed by MIT in Cambridge (Qing Hu). SRON will also incorporate unique devices for the frequency stabilization from the Institute for Physics of Microstructures, in Nizhny Novgorod (Dmitry Pavelyev).
The principal investigator of the GUSTO mission is Christopher Walker from the University of Arizona. Co-investigator Jian-Rong Gao (SRON & TU Delft) will lead the project in the Netherlands. Floris van der Tak (SRON & University Groningen) and Xander Tielens (University Leiden) will contribute to the science team.