STO2 landed and data secured

The STO2 first light spectrum at 1.9 THz. Credit: Delft University of Technology

https://phys.org/news/2017-01-sto2.html

The STO2 telescope with Dutch detectors on board that circled around the South Pole in December 2016 to investigate gas clouds between the stars landed safely on 30 December.

At an altitude of 39 kilometers the NASA telescope circled along with the polar vortex for a period of three weeks. During that time STO2 picked up as much radiation as possible at the frequencies of 1.4 and 1.9 THz to find ionized nitrogen (NII) and ionized carbon respectively (CII) in a part of our Milky Way. These substances indicate the process of star formation from dust and gas.

Measuring oxygen

The 4.7 THz detector that would measure neutral atomic oxygen (OI) also worked. However, something went wrong in the system for the local oscillator that had to generate the required reference signal of 4.7 THz. An electrical component needed for the communication between this local oscillator and ground control became overheated by the sun. OI reveals that a star is actually being born. This is an observation that astronomers are keen to obtain, especially if that observation is being done for the first time beyond the earth's atmosphere, as would have been possible with STO2.

STO2 project leader for SRON and TU Delft researcher Jian-Rong Gao and his team are indeed disappointed about the absence of the 4.7 THz observations but on the other hand they are extremely happy with the large quantity of data for the other two frequencies. After an initial hiccup in the orientation mechanism of the telescope, the collection of that data proceeded really well. "Once the rough data have been processed to reveal spectral lines for CII and NII then STO2 will have drastically expanded the area mapped so far for these substances."

Mission continues

STO2 was launched from Antarctica on 9 December 2016. The polar vortex also ensures that the balloon missions land again at a location that can be reached along the South Pole Traverse, a sort of Antarctic 'motorway' between the South Pole and McMurdo. When the cooling fluid for the superconducting detectors (liquid helium) had been used up and the data was safely downloaded to computers on earth, STO2 landed on the South Pole Transverse. The telescope was picked up on 10 January so that it could be brought back to McMurdo.

STO2 is an exploratory mission under the leadership of the University of Arizona for astronomy in these terahertz frequencies. On 24 January 2017, NASA will visit the University of Arizona to decide about GUSTO. This is also a balloon mission but with a longer duration (about 100 days) and with more effective instruments on board. For NII, CII and OI, GUSTO will have cameras with eight pixels that will once again be developed by SRON and Delft University of Technology.

The teams of professor Alexander Tielens (Leiden University) and professor Floris van der Tak (SRON/University of Groningen) will contribute to the scientific analysis of the observations.

Polar balloon STO2 to go the edge of space with Dutch instruments

Credit: Jian-Rong Gao
http://phys.org/news/2016-12-polar-balloon-sto2-edge-space.html

Stars and planets are born from clouds of molecules that coagulate and eventually fall apart again in the space between the stars in a galaxy. Astronomers still do not know exactly how this works.
That is why NASA's stratospheric balloon STO2 will be launched from Antarctica to the edge of space to measure cosmic far infrared radiation. At an altitude of 40 kilometers above Antarctica, the air is crystal clear. There is scarcely any water vapor, which often blocks this type of radiation at other locations in the atmosphere.

The NASA balloon that will carry the measuring instruments to this altitude will make use of the circular polar vortex, a stable airflow on which the balloon can circulate with for one or more rounds of about 14 days each.

This will allow scientists to carry out observations for a period of two weeks before they find the balloon at nearly the same location again. STO2 has been developed under the leadership of the University of Arizona and contains vital contributions from SRON Netherlands Institute for Space Research (Utrecht and Groningen) and tech university TUDelft. These are three receivers for 1.4, 1.9 and 4.7 terahertz respectively.

Spectra of radiation at these frequencies often disclose the presence of elements in space, including electrically neutral atomic oxygen. The localization of that last element in space, which can be achieved using the 4.7 terahertz receiver, is a long-cherished dream of astronomers. It is the first time a 4.7 terahertz receiver will be brought to the edge of space for an unrestricted view. Together with the Massachusetts Institute of Technology (MIT), the partners developed a reference source for radiation at this frequency. Electrically neutral atomic oxygen reveals us places in the gas clouds between stars that are particularly warm.

Credit: Delft University of Technology

This is a good indicator for stars that only just formed. This way we can directly find the birthplaces of new stars. STO2 is therefore an important scouting mission for future terahertz missions using a satellite in space. Far infrared radiation is sometimes also referred to as terahertz radiation. One terahertz is equivalent to a wavelength of 300 micrometers. The University of Arizona is scientifically in the lead of the mission. The teams of prof. dr. Alexander Tielens (Universiteit Leiden) and prof. dr. Floris van der Tak (SRON/Rijksuniversiteit Groningen) will help in the international scientific analysis of the observations. Thursday the team on Antarctica gets three hours of good weather conditions. If this is too short, nice launching weather will follow in the following days.