Waiting for wind

Dr. Jian Rong Gao reports from Antarctica where he waits for the NASA balloon launch of the STO2 mission. His group has made the terahertz detectors on board.

UPDATE December 09, 2016 – The STO2 mission has succesfully been launched on Thursday December 8, 22:00 Dutch time. Its trajectory is shown here.

Gao wrote: ‘I am in Antarctica this year for STO2. Arriving at the ice with US Air Force C17 cargo is really cool. I feel it is a privilege to be here. I arrived at 17th Nov and will leave from McMurdo on 8th. Many other Americans are surprised to hear that the Dutch have contributed most of the key technology in STO2.’

‘Yesterday we finished all the assembly and test, and performed a so-called hang-test. Essentially it is the final checking of the communication and functionality when STO2 was taken out the hangar. In the old days, if this was done, it immediately went to launch pad to lift the balloon up. Now we need to wait for a launch window; the expectation is the morning this Thursday, but we are never sure.’ That was last Tuesday.

The NASA Long Duration Balloon research strongly depends on the polar wind. The wind should to pick up the balloon at 30-40 kilometres altitude and carry it counter clockwise around the South Pole. But it’s critical. There are strict demands to the wind force (neither too weak nor too strong) and to the stability over time as well as with altitude. And then there is visibility: when snow falls, no launches take place.

That polar wind has started early this year, Gao reports. It picked up at the end of November so that two of the balloon missions, BACCUS and ANITA IV, were launched last week. Their position is tracked on a NASA website.

The launch of the Stratospheric Terahertz Observatory (STO2) from the University of Arizona has now been scheduled for early Thursday evening (Dutch time) with a second opportunity on Friday when the weather looks even better according to the local meteorologist.

TU in space
TU in space

TU in space

So what is the role of TU Delft in all this? Mission leader Professor Christopher Walken (University of Arizona) has ordered the terahertz sensors from Dr. Gao’s lab at the section quantum nanoscience from the TU Delft Faculty of Applied Sciences (TNW). Gao has a long history of making terahertz sensors for example for the ESA Herschel mission (2009-2013). “We are the eyes of the mission,” Gao stated in a previous article on STO2.

The terahertz sensors will scan a part of the Milkyway (about 10 degrees wide) for traces of oxygen. To astronomers, the oxygen spectral line means a temperature of about 300 Kelvin. In contrast with a background of 100 Kelvin, the local heat indicates the birth of a star.

Last year, the STO2 mission waited until past Christmas and into the New Year for an opportunity to launch, but to no avail. The mission was aborted in January 2016.

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