Ulysses Neutral Gas Experiment

Determination of the velocity and temperature of interstellar neutral helium

The ULYSSES spacecraft launched with a NASA Space Shuttle in October 1990 carried on board the GAS-experiment which was designed to measure the local angular distribution of the flow of interstellar neutral helium in the inner heliosphere. The composite picture shows the heliosphere as seen from the ULYSSES GAS instrument in January 1992 inbound toward Jupiter.
The flow of interstellar neutral helium appears as the blurred spot at longitude lamba ~ 225° , latitude beta ~ 5°. At lamda ~ 135°, beta ~ 1° the neutral emission from Jupiter and a chain of UV-stars along the galactic plane in the southern hemisphere can be seen.
The instrument consists of two detection channels which are identical except for their field of view. Two circular apertures define a conical field of view ( 7.40 full width). Particles entering this field of view impact on a target surface coated with thin layers of lithium-fluoride. This leads to an emission of secondary particles, electrons and/or ions, which are accelerated into the funnel of a CEM. The events are subsequently counted by conventional electronics.

(M.Witte, H.Rosenbauer, M.Banaszkiewicz und H.Fahr,
Adv.Space Res.Vol. 1 3,No.6, pp.(6)121-(6)130,1993).

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