The scientist who came in from the cold

A giant balloon carrying the gondola with the stratospheric terahertz observatory STO2 was launched on December 8, 2016. That was one day after Dr. Gao’s departure from Antarctica. He flew with a military C130 to Christchurch, New Zealand, then to Sydney and on to Los Angeles. Upon arriving at Los Angeles, Gao tried to get signals from his sensors on board of the balloon. There was something wrong; The colleagues in Antarctica told him. They were working on it.

Back in Delft, four days after the launch, Gao wrote: ‘No spectrum yet. The instrument part is working fine, and the Dutch THz receivers are working well. But the wide-field star track cameras have an issue, seeing unexpected stray light, causing problems with pointing the telescope. The people from Applied Physics Laboratories (APL) are working hard on it.’

Slow process

The Star Track system didn’t work. It should point the telescope to exactly the right place in the sky, but it didn’t. So, the engineers decided for a software update. But that proved to be a painfully slow process because of the limited bandwidth. Gao said: “It is like working with the earliest internet from a telephone line. You hit Return and think: come on!”

Another two days later, they succeeded in restoring the Star Tracker and STO2 produced ‘First Light.’ Gao wrote: ‘Since last Thursday, it was officially claimed that STO2 is working as an observatory. It took a while to solve the issue. Please see the first light spectrum at 1.9 THz of STO2 from the Statue of Liberty Nebula.’

First Light

First Light

First Light

The graph he sent shows the emission spectrum at 1.9 THz that is indicative of the presence of carbon. The red line shows to where the telescope was pointing (Can you recognise the Statue of Liberty in the clouds?).

The STO2 spectrum was verified against a measurement from 1997 by scientists Boreiko and Betz. That graph took 10 minutes of integration time; the terahertz sensors from Delft only needed 6 seconds. In other words: the new sensors are 100 times more sensitive (or faster).

Waiting continues

So, is the mission accomplished? Not quite yet. Gao is still waiting for mission control to switch on his third sensor. Currently, sensors for 1.4 THz and 1.9 THz are active. They measure the presence of nitrogen and carbon. The third sensor (4.7 THz) is tuned to oxygen. Gao knows there should be enough helium on board for another seven days. And so the waiting game continues, but the worst anxiety is over.

“I was too excited the whole time to feel tired. Now I’m beginning to feel the jetlag”, Gao admitted. Luckily, it’s almost Christmas.

Read also:

Report from the pole

Overview article on the STO2 mission

How the detectors work

What’s next?