The mission shown here was the Stratospheric Terahertz Observatory (STO), launched on January 15, 2012 from Antarctica. It studied large dense molecular clouds in the southern sky of the Milky Way. The BRRISON mission, explained here –
(http://go.nasa.gov/1bDq2xP) is using many of the STO subsystems (computers, pointing, and stabilization equipment).
At an altitude of 40 kilometers, the sky is crystal clear. There is hardly any water vapor, hardly anything disturbing at all: the edge of space is a perfect environment for doing astronomical observations. NASA uses super pressure balloons to lift observatories to that height. TU Delft is developing a terahertz receiver for such a balloon observatory.
In 2012, the Stratospheric Terahertz Observatory (STO) circled Antarctica in 14 days, using the stable polar wind. On board was a 0.8 meter telescope for observing the interstellar medium – the material between the stars – and the life cycle of interstellar clouds. Terahertz measurements are hard to do from the ground because of the water vapor in the atmosphere.
The mission was a success, so NASA decided to fund its successor STO2. As leading experts in the field of terahertz receivers, Delft University and SRON are being asked to deliver a new 4.7 terahertz receiver. No one has ever flown such a receiver at this frequency, so this new channel on STO2 is a proof-of-concept. “The 4.7 terahertz receiver can map neutral atomic oxygen, a longstandig dream of astronomers. Missions with terahertz receivers will provide them with missing pieces in the puzzle of the life cycle of galaxies”, says team leader Jian-Rong Gao. The project is a collaboration between TU Delft and SRON. Gao regards the project as an important stepping stone mission to space.
The detector is based on a so called single pixel superconducting hot bolometer (HEB) mixer, the most sensitive heterodyne detector available in the terahertz domain. A quantum cascade laser, developed through a collaboration with MIT, is needed to provide a reference frequency for the incoming signals from space. The balloon will be equipped with a 90 liter liquid-helium tank and a 60 Kelvin cryocooler to keep the system at the right temperature. The hold time of the cryostat will limit the observation time to a maximum of 40 days.
Jian-Rong Gao, email@example.com, Quantum Nanoscience Department, Faculty of Applied Sciences.
More information: gaolab.tudelft.nl