KTH logo


... an X-ray balloon-borne polarimeter for astrophysics



2016-07-18 Landing @ 22h26 UTC

Early this morning, at 00:26 local time, PoGO+ touched down safely by parachute on Victoria Island. The flight has gone extremely well. We conducted 7 observations of the Crab and 6 observations of Cygnus X-1. Observing conditions were excellent and we are looking forward to starting the analysis of the data once it is returned to Sweden.

2016-07-12 Launch @ 03h17 UTC

After waiting for the winds to slow down, PoGO+ was launched at 05:17 local time. All is working well - the balloon is at 39628 m - and we are observing the Crab.


2016-07-01 PoGO+ is ready!

The polarimeter is fully assembled and integrated to the gondola.

2016-05-13 PoGO+ is shipped to Esrange

2015-09-29 PoGO+ is under construction

PoGO+ is now under construction at KTH royal institute of technology. The new detectors, SDCs, are finished and are being tested for performance and light tightness. The bests 61 out of the 79 produced will be selected and positioned in the instrument like in this picture. The collimators are being build and will cover all of the detectors.

The projectThe project


PoGOLite and PoGO+ : balloon-borne hard X-ray polarimetry

In the PoGO missions, an X-ray telescope built at KTH is lifted to an altitude of about 40 km suspended under an enormous (1.1 million cubic metres) helium-filled balloon. The balloon is launched from the Esrange Space Centre in Northern Sweden. A high altitude is needed since X-rays are absorbed by the earth's atmosphere. X-rays are a form of electromagnetic radiation, just like visible light or radio waves. The polarisation of a wave describes how the oscillation of the wave is oriented with respect to the wave’s motion. Check your sunglasses - the lenses may be polarised. On a sunny day you’ll notice a glare on the sea as sunlight is reflected towards your eyes. You can remove much of this glare by putting on your polarised sunglasses. This is because the reflected light waves become polarised as they ‘bounce off’ the surface of the water and your sunglasses are designed to block these polarised waves. The PoGO missions measure the polarisation of X-rays emitted by high-energy sources on the sky, such as pulsars and black hole systems.


Pulsars are fascinating objects - imagine a giant neutron-rich atomic nucleus, 15 km in diameter and with a mass comparable to the Sun. This particular pulsar rotates around an axis 30 times per second producing flashes of X-rays on the sky like a cosmic lighthouse. Detecting these X-rays is nothing new and there are a number of satellites currently in orbit which routinely study astronomical objects in this way. What PoGO+ brings to the table is a new way to make observations since the polarisation of the X-rays can be measured and this tells us about the environment in which the X-rays are produced - for example, the magnetic field configuration. Such information is ambiguous when inferred from ‘standard‘ X-ray observations. For this reason, X-ray polarisation measurements are often said to “open a new window on the universe”.

In July 2013, the PoGOLite X-ray telescope almost completed a circumpolar flight around North Pole. This was a "Pathfinder" flight which aimed to test the telescope design and make first observations of the Crab - a pulsar and nebula system - located in the constellation of Taurus some 6500 light years from the Earth.

During summer 2016, PoGO+ (an improved version of PoGOLite) returned to Esrange for another balloon flight. The aim of PoGO+ is the same as PoGOLite, i.e. to study the high energy light (X-rays) emitted by the Crab. A black hole binary system, Cygnus X-1, was also observed.

Who's involved?

The PoGO missions are lead by the Astroparticle Physics group within the Physics Department at KTH Royal Institute of Technology. Important contributions are also made by Hiroshima University in Japan, and the Stockholm University Astronomy Department. The PoGO attitude control system was developed in conjunction with DST Control (www.dst.se) and SSC (www.sscspace.com) developed the PoGO gondola, power and communication systems. The balloon launch is conducted at the SSC Esrange Space Centre.

Further information

More information can be found in the publications section.

External links






The stamps

PoGOLite was featured on two stamps issued by the Swedish post office in January 2009 to mark the International Year of Astronomy. A number of first-day covers featuring the stamps were flown on the 2013 flight.

Link (in Swedish): http://sff.nu/postnord-slapper-rymdbrev/


Swedish participation in PoGOLite was made possible through a grant awarded in 2005 by The Knut and Alice Wallenberg Foundation. Now-a-days, the PoGO missions are supported by the Swedish National Space Board. The Swedish Research Council funded work on the attitude control system. Several PoGOLite team members receive salary support from The Swedish Research Council or The Swedish National Space Board. The Göran Gustafsson Foundation has funded work on the star tracker systems. Support has been recevied from KTH in the form of faculty research funding.