Solar Physics: Ulysses and ACE

The Department of Space Research, University of Birmingham, UK is a member of the instrument consortium for the Heliospheric Instrument for Spectra, Composition and Anisotropy at Low Energies (HI-SCALE), one of the instruments carried by Ulysses. It is also a member of the instrument consortium for the Electron, Proton and Alpha Monitor (EPAM) which was the HI-SCALE flight spare and is carried by the ACE spacecraft.

Ulysses		ACE
The Ulysses spacecraft, launched in 1990, used Jupiter's gravitational field to enter a high inclination orbit of the inner heliosphere. A suite of 12 different instruments carried by Ulysses allows us to study, in-situ, the interplanetary magnetic field, solar wind, solar cosmic rays, solar radio emission, solar X-rays and cosmic gamma-rays. Since Ulysses became operational, its unique trajectory combined with its comprehensive instrumentation has allowed us to build up a detailed picture of the 3-dimensional heliosphere over an entire solar cycle. Ulysses is a project of international co-operation between ESA and NASA.		The ACE spacecraft was launched in 1997 and placed in a halo orbit about the L1 point between the Sun and the Earth. The L1 point occurs where the gravitational field of the Sun and the Earth are equal and opposite. Consequently ACE is well placed to observe a range of Earth directed solar activity making it an important component of Earth's early warning system for geomagnetic disturbances. ACE carries a suite of 9 different scientific instruments many of which have a similar design to those on Ulysses. The Ace mission was designed and developed under the support of NASA's Explorer Program.