June 1980:space activities report

TWO-COMET MISSION

NASA, in cooperation with the European Space Agency, is asking scientists to propose experiments for a planned international mission to two comets - Halley and Tempel 2. The total journey will span four years and cover more than 2,500 million kilometres (1,600 million miles).

Utilizing solar electric propulsion engines for the first time in deep space, the spacecraft will fly past Halley’s Comet in 1985, release an instrumented probe toward the comet and then go on to encounter Tempel 2 in 1988 and fly side by side with it for a year or more as Tempel 2 swings round the Sun.

Closeup pictures and other scientific information returned by the spacecraft are expected to add significantly to our knowledge about comets, which in turn may shed more light on the origin and evolution of the Solar System.

NASA emphasized that the project has not yet been approved but that early selection of scientific participants and investigations is required for a prompt start if approval is granted.

Under current plans, NASA will be responsible for the launching, rendezvous spacecraft system and mission operations. The European Space Agency will be responsible for the Halley probe system. The combined scientific payload will be shared by scientists throughout the world.

The proposed mission has three major science objectives:

• To determine the chemical and physical nature of the comet's nuclei.

• To characterize the chemical and physical nature of the comas,the gases and dust which surround the nuclei

• To determine the nature of the comets' tails.

Instruments on the Halley probe and the rendezvous spacecraft will sense the comets remotely as well as collect dust and gases for onboard analysis.

The Halley/Tempel 2 comet mission will be launched by aSpace Shuttle in July 1985. The spacecraft will be propelled in deep space by ion (solar electric) propulsion, a new fuel-efficient technology system now under development by NASA.

The spacecraft will encounter Comet Halley in November 1985, about 120 million km (75 million miles) from Earth, and eject a probe that will plunge into the coma, returning a variety of data. At that time, Comet Halley will be travelling relative to the spacecraft at a speed of 57 km/sec (127,000 mph). .

The probe will pass within 1,500 km (930 miles) of the nucleus. Data acquired by the probe will be transmitted to Earth via the spacecraft. The spacecraft will then pass 130,000 km (81,000 miles) on the sunward side of the nucleus, and head for Tempel 2.

At Tempel 2 rendezvous, the spacecraft will approach the comet at a distance of a few thousand kilometres, well outside the theoretical "dust hazard” envelope, and assess the hazards. If all looks well, controllers will command the spacecraft to proceed to within 100 km (60 miles) and finally to within 50 km (30 miles) of the nucleus. The spacecraft will stay with Tempel 2 for a year or more, obtaining high-resolution pictures and other measurements of the nucleus and other cometary parts. The onboard cameras may ultimately be able to detect objects as small as a baseball on the surface of the nucleus.

The Jet Propulsion Laboratory, Pasadena, California, will manage the mission for NASA’s Office of Space Science,Washington, D.C. The laboratory, a government-owned facility operated for NASA by the California Institute of Technology, also will be responsible for a rendezvous spacecraft system and mission operation. A European Space Agency project team will be responsible for the Halley probe. The design, development and implementation of the mission will involve the direct interaction of NASA and the European project teams and a Project Science Group composed of principal investigators, team leaders and selected interdisciplinary scientists.