NASA’s GUSTO balloon telescope has launched from Antarctica on December 31st. The far-infrared observatory carries out the first large-scale survey with velocity-resolved imaging of the spectral lines emitted by three cosmic elements between stars. GUSTO is equipped with three 8-pixel cameras. SRON and TU Delft made one of those and contributed to the other two.
NASA’s Galactic/Extragalactic ULDB Spectroscopic Terahertz Observatory (GUSTO) is a balloon observatory that will keep drifting and circulating in the Earth’s atmosphere at 36 km altitude above Antarctica for 55 days. The observatory is carried by an Ultra-Long Duration helium balloon with the size of a football field and consists of a telescope one meter in diameter and a cryogenic instrument with superconducting detectors operating at -269 °C. GUSTO carries three array receivers for far-infrared radiation of 1.4, 1.9, and 4.7 terahertz to detect and map emission lines of respectively ionized nitrogen [NI], carbon [CII], and oxygen [OI] in the interstellar medium (ISM)—the gas and dust in between stars. SRON built the oxygen camera and contributed to building the other two.
Calm conditions
In order for the launch to go ahead, calm conditions are required on the notoriously rugged continent. Therefore the first launch attempt was only planned shortly in advance. Wind speeds may not exceed 10 km/h, while the wind direction must be the same everywhere between the ground and 300 meters altitude. Furthermore, the circumpolar vortex must have formed in the stratosphere above Antarctica. In the end, the researchers found the perfect circumstances on December 31st.
Vortex
The vortex allows GUSTO to float circularly at an altitude of 36 km. Normally speaking it will last longer than 55 days. However, once the vortex breaks down, GUSTO will spiral outwards, and the observation efficiency will decrease slowly because of an increased temperature difference between day and night and a reduced electrical power from the solar panels. Eventually, GUSTO will be terminated and likely drop into the ocean or on Australia or Antarctica.
GUSTO is led by the University of Arizona. SRON and TU Delft (Faculty of Applied Physics) delivered the so-called Hot Electron Bolometer multi-pixel (heterodyne) cameras and a novel phase grating for creating a multi-beam local oscillator originated from a single 4.7 THz quantum cascade laser. The local oscillator helps the detectors to determine the exact color of the incoming far-infrared light. Furthermore, Jose Silva on behalf of the Dutch GUSTO team is on the scene to contribute the GUSTO’s Antarctica flight campaign.