A perfect view of the Milky Way

On a series of calm, cool mornings in April 2017, 70 French scientists (from the French space science agency CNES, CNRS IRAP, and the Université Paul Sabatier de Toulouse) launched three enormous balloons into the sky above the heart of Australia.

CNES was using the Alice Springs Balloon Launching Centre (ASBLS) to send three precision scientific instruments up to altitudes of 30–40 kilometres to make observations that are impossible from the ground.

CLIMATE studied the concentration of greenhouse molecules in the upper atmosphere; CARMEN provided imagery of the stratosphere to measure aerosols, cloud, smoke and dust; and PILOT mapped the magnetic polarisation of dust clouds in our galaxy.

“The helium-filled balloons carrying the instruments can be the size of the Melbourne Cricket Ground, about a million cubic metres in volume, when at float altitude. They are expensive to make, and very complicated to launch, but they can achieve science that cannot be done on the ground,” says Dr Ravi Sood, Director of the ASBLS.

“X-rays and gamma rays emitted from neutron stars and black holes are almost totally absorbed in the top of the atmosphere so we cannot observe them from the Earth’s surface. The only way to do this kind of astronomy is by sending detectors to the edge of space and stratospheric balloons are perfect for the job.”

The ASBLS is run by NASA, CSIRO and University of New South Wales, but organisations such as CNES also use the facility.

Ravi says that Alice Springs is a special place.

“Australia is great for observing our Milky Way Galaxy because its centre passes almost directly overhead, and you cannot see it from the Northern Hemisphere. Combined with predictable weather, vast tracts of open land and great infrastructure such as downwind tracking stations, there are few places in the world like this.”

Banner image: The PILOT balloon being readied for launch. Credit: Sébastien Chastanet – OMP / IRAP / UT3 / CNES / CNRS