The High-Energy Transient Explorer (HETE-2) The rocket carrying the High-Energy Transient Explorer (HETE-2) lifted off at 06.38 on Monday from the Kwajalein Missile Range in the Marshall Islands. HETE-2 is now in a stable orbit around 600 km above the Earth.

The US / French / Japanese HETE-2 satellite is designed to detect and track down Gamma-Ray Bursts (GRBs). These are the most energetic events in the universe since the Big Bang and take place at large distances from our milky way galaxy. Their origin is still poorly understood – scientists have a variety of theories such as the merger of neutron stars or unusually bright supernovae described as hypernovae.

On average a GRB takes place every day, but it can only be detected from instruments in orbit as the Earth’s atmosphere prevents gamma rays from reaching the ground. GRBs may only last a few seconds which leaves little time to pinpoint their location and hence arrange follow-up observations with ground-based telescopes around the world. HETE-2 will be able to pinpoint the location of the burst to a circle of 10 arc seconds or about 1 / 200 the size of the Full Moon. This is around 10 times better than any previous detector. Its location will then be sent to optical and radio observatories around the world within a few minutes of the burst taking place. Astronomers can then aim to match its position with a more familiar setting such as a spiral arm in a distant galaxy. In this way the site of the burst can be viewed soon after it takes place and with luck its fading light or radio emission may still be visible.