THE HUBBLE
TECHNICAL
MATTERS
· Hubble gets
servicing in space
The Hubble Space Telescope (HST) was initially schedules to return to Earth for refurbishment and be relaunched every five years, but concerns about contamination led to a change of plan. NASA decided that on-orbit servicing would be adequate to maintain the 15-year design life of HST and a three year cycle of servicing was adopted, with successful mission completed in Dec 1993 and Feb 1997. In Dec 1999, the 1970s era Fait Object telescope will be replaced by the advanced Camera for Surveys which can offer twice as much detail and a larger view of the sky. A fourth servicing mission is planned for mid 2002.
· COS lets astronomers
look back billions of gears
When Hubble is next serviced, in 2002, scientists will install the Cosmic Origins gather light from distant stars, galaxies and quasars, allowing astronomers to study the very early Universe. About the size of a telephone box, the COS is 20 times more sensitive than anything currently in operation, and will offer a glimpse of how galaxies and chemical elements were formed 10 billion years ago. It will be constructed at the University of Colorado, USA, and is expected to cost around $25 million.
· Preparation for the
next space telescope
Plans are already under way for Hubble’s successor, the Next Generation Space Telescope (NGST. The NGST will be larger than the HST and its primary goal is to study the very early Universe. The NGST will be up to 1,000 times more sensitive, partly because it will orbit the Sun rather than the Earth. It will cost $500 million, and it is likely that a further $400 million will be spent over its planned 10 year lifetime. Four designs are being considered, and a decision is expected in 2002, with construction beginning the year after. The Space Telescope Science Institute in Baltimore, Maryland, USA, will manage the NGST science programme.
OBSERVATIONS
· Hubble photographs
aurorae on Saturn
The HST has beamed back UV images of Saturn’s aurorae from the Space Telescope imaging Spectrograph. They are ten times sharper than earlier pictures, and show charged particles steaming from the Sun and striking the planet’s atmosphere, where they excite molecules and make them glow. They will help to work out the composition of Saturn’s atmosphere, Astronomers still cannot explain two bright streaks between the atmosphere and Saturn’s moon.
Hubble captures
the biggest star
In Oct 1997, Hubble’s NICMOS captured an image of what might be the brightest star in the Milky Way. It has been named the Pistol Star because of the shape of its nebula, and it appears to be 100 times larger, and 10 million times brighter, than the Sun. The giant star, which is hidden away deep amid dust clouds near the centre of the galaxy, is exhausting fuel at a dramatic rate, which means that it is likely to die in a spectacular explosion within three million years.
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