Aboard the world’s highest telescope
Seeing an aurora from the world’s highest telescope was the highlight of a great night for astronomer Ian Griffin.
At 5pm on Sunday, July 17, like thousands of other people each day, I boarded an aircraft at Christchurch International Airport. However, unlike every other departure I have made previously from Otautahi, my destination on this particular trip wasn’t Dunedin, nor indeed Wellington or Auckland.
Instead, along with about 30 astronomers, technicians, teachers, observers and, most importantly, three NASA test pilots, I climbed aboard Sofia, the Stratospheric Observatory for Infrared Astronomy, a US$1 billion ($1.43b) Us/german flying observatory destined to take us into the stratosphere.
During our flight, Sofia reached a height of more than 12km above the southern ocean. At this altitude, more than 99.8 per cent of the water vapour in Earth’s atmosphere is below the observatory’s 17-tonne telescope, which means it can study astronomical targets at infra-red wavelengths, which the vapour blocks from reaching telescopes on the ground.
Our mission was to study a variety of objects in the southern sky using the largest telescope in New Zealand – a title temporarily wrangled from the Mount John Observatory during Sofia’s time here.
Wheels up was at 5.49pm. For the next 10 hours I became the astronomical equivalent of a child in a sweet shop, as I watched in awe the skilled team operating the Boeing 747SP aircraft. Shortly after takeoff, a whole section at the rear of the aircraft opens so that sophisticated detector systems behind the 2.5-metre diameter telescope can capture scientific data.
On this particular mission, astronomers were using the telescope to study a number of interesting targets, including Nova Sagittarius 2015, a binary star which brightened massively in 2015, and Eta Carina, a massive star system which may become a supernova at some point in the next few thousand years.
Accurately pointing Sofia’s telescope at a moving target star from a moving aircraft in a turbulent flight environment is a triumph of design, technology, teamwork and excellent planning.
Put simply, whether on the ground or in the air, to find an object in the sky you need to move a telescope either up or down, and left or right.
In the case of Sofia, the onboard technical team controls the ‘‘up or down’’ part of the pointing and the aircraft pilots control the ‘‘left or right’’ part.
On this flight there was constant communication between the pilots and technical team to ensure light from the celestial targets was placed accurately on the sensitive infra-red camera system used by the onboard astronomers to study their celestial prey.
The resulting flight paths for Sofia missions are therefore mixtures of long, gentle curves or straight lines, separated by sharp turns when a new target is selected.
During our mission we got as far south as 62 degrees, and we crossed the International Date Line twice. So in 10 hours, Sofia actually ‘‘visited’’ three different days – the flight took off on July 17, crossed the date line back to July 16, where we stayed past midnight which meant we were back into July 17, after which we re-crossed the date line and it became July 18.
The science being done on Sofia was compelling but I have to confess to spending much of the flight taking photographs through the windows.
I visited the flight deck and took some pictures of an extraordinary display of the aurora australis, and then had stunning views as Sofia descended into Christchurch.
On the final leg of the flight we were at 44,000 feet (13km) which is much higher than most airliners fly, and I also managed to get some pictures of Dunedin and the Southern Alps on a night when the moonlight was very bright.
Despite landing in Christchurch at 3.30am more than a week ago, my feet still haven’t touched the ground.
Dr Ian Griffin is an astronomer and the director of Otago Museum.