Tim Furniss/LONDON
The $2 billion Next Generation Space Telescope (NGST), which is to succeed the Hubble Space Telescope (HST), faces a two-year launch delay until 2009. The delay is necessary for the development of new technologies to allow the NGST to meet its science goals and for two precursor missions to be launched.
Space Shuttle mission STS112 will be flown in October 2001 to test the deployment of the NGST's sunshade and boom from the Shuttle's payload bay. The Inflatable Sunshade in Space experiment will use inflatable structures which may not necessarily be used on the final NGST version.
The second precursor mission will be made by the Nexus spacecraft, fitted with a 2.8m (9.2ft)-diameter telescope modelled on the larger instrument to be flown on the NGST. The HST's primary mirror is 2.4m in diameter, while that planned for the NGST will measure 8m across.
Nexus, which will test telescope technologies, will be placed into the NGST's planned operational orbit, 1.5 million km (932,000 miles) from Earth where it will appear to be in a stationary position between the Earth and the sun. The telescope will require a large sunshade to block light from the sun, keeping the telescope dark and at the temperatures required for the NGST's three instruments - a visible-infrared spectrometer, a mid-infrared camera spectrograph and a multi-object spectrograph.
The NGST, which has been described by the National Academy of Sciences as the highest-priority astronomy project in the next decade, will have to use new mirror technologies to enable the 8m diameter mirror to be flown as no expendable launch vehicle can fly with a payload shroud large enough to accommodate it. The NGST will not fit inside the payload bay of the Space Shuttle, which has a maximum diameter of 6.7m. The mirror will have to be folded and unfurled in space or made up in sections to be assembled in space. Technologies being studied include thin mirrors supported on fibre ribs and beryllium mirrors.
The NGST is manifested tentatively for a Delta IV launch. Two industry teams, Lockheed Martin and TRW/Ball Aerospace, are working on NGST designs and a prime contractor will be selected in September 2001.
• The next Hubble Space Telescope servicing mission by Space Shuttle astronauts next June will include work to restore the telescope's Near Infrared Camera and Multi-Object Spectrometer, which exhausted its supply of nitrogen ice coolant in 1999.
Source: Flight International
