NASA’s Scientific Balloon Program, with support from the National Science Foundation’s United States Antarctic Program, conducts an annual launch campaign November into February in Antarctica, a continent known for multiple extremes: the coldest, driest, and windiest of all. The payloads and instruments flown during the campaign are solar-powered, making this time of year an ideal time for balloon flights since the region experiences sunlight 24-hours a day during the Antarctic summer. In addition, a weather phenomenon during the Antarctic summer known as an anticyclone takes the balloon on a circular flight trajectory, keeping the balloon over the Antarctic land mass over extended periods of time. Keeping the balloon over land helps enable recovery of the payload at the conclusion of the mission. Learn more about NASA’s Super Pressure Balloon technology and the type of science we fly during our Antarctic campaign in this short, 10-minute documentary. (Credit: NASA/Bill Rodman).
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