Giotto's suicide mission: The European spacecraft that had a close encounter with a comet is not likely to survive its second, says Peter Bond

THIS WEEK a new chapter in the history of space exploration will be written when Giotto, the first European craft to be sent into deep space, will visit its second comet in six years.

Until now, only two comets have been examined at close quarters by instrument-laden spacecraft. In September 1985, in the first encounter of its kind, the International Cometary Explorer flew through the tail of Giacobini- Zinner, a very old, quiet comet. The spacecraft carried no camera and simply measured electrical and magnetic fields.

In March 1986, Giotto swooped past Halley's Comet, barely surviving prolonged exposure to an intense rain of fast-moving particles as it sent back the first close-up pictures of a comet's nucleus. On Friday this redoubtable explorer, which was built by British Aerospace and a team of contractors from nine other countries, will be subjected to a second, probably fatal, dose of the same medicine.

The latest target for Giotto's instruments will be Comet Grigg- Skjellerup, named after its co-discoverers. It was first seen by John Grigg, a New Zealander, in 1902 but was subsequently lost until May 1922, when it was recorded by a South African, John F Skjellerup. When it was realised that the two sightings were of the same object, the work of both men was given equal recognition and the comet duly acquired its ungainly name.

Comets are of particular interest because they are thought to contain the primeval raw materials from which the planets were formed four-and-a-half billion years ago.

Just like moths attracted to a flame, these small balls of snow and ice shorten their active lives each time they return to the infernal regions near the Sun. Their surface layers evaporate, creating wispy tails that stream millions of kilometres into space.

However, Giotto's two cometary targets could hardly be more different. Grigg-Skjellerup approaches the inner solar system every five years, while Halley's much-trumpeted visits to our skies occur once every 76 years. Whereas Halley's much larger, relatively pristine nucleus still retains sufficient icy material to present magnificent celestial illuminations, Grigg-Skjellerup has lost its youthful vigour.

According to Andrew Coates of the Mullard Space Science Laboratory in Surrey, it is much smaller and older than either of the comets so far visited. Its mile-wide nucleus is only hidden by a small coma of dust and gas because most of its volatile ingredients have long since boiled away.

Although Dr Coates expects Grigg-Skjellerup to develop small versions of the dust and plasma tails normally associated with its more active brethren, he believes that its interaction with the surrounding environment, especially with the solar wind of charged particles emitted by the Sun, will be much less marked.

The nature of its orbit also makes Grigg-Skjellerup different. It belongs to a fairly small group of about 100 comets that orbit the Sun in the same direction as the planets. This means that Giotto will be able to overhaul its target at the relatively leisurely pace of nine miles per second.

In contrast, Halley's Comet travels in the opposite, or retrograde, direction around the Sun. Giotto and Halley's Comet hurtled past each other at a velocity of 42 miles per second, like two supersonic aircraft.

Nevertheless, Giotto's unique vantage point, 375 miles from Halley's nucleus, enabled it to unveil the black, encrusted surface and brilliant gaseous eruptions taking place at the heart of the comet. For the first time, the true nature of one of the solar system's building blocks was revealed.

Not surprisingly, few scientists expected the craft to survive the ordeal as it was bombarded by dust particles travelling 50 times faster than the speed of a bullet. These fears seemed to have been borne out when the screen at mission control went blank one minute before the closest approach. In fact, Giotto was knocked spinning by an impact with a 'large' dust particle of about a gram in mass. More than half an hour passed before reliable contact was re-established.

After a preliminary check of the spacecraft's condition, it was put into hibernation until its orbit would carry it back to the vicinity of Earth and a decision could be made about targeting it towards a second comet. Contact was re-established on 19 February 1990 when Giotto was about 60 million

miles from home. Ground controllers were able to turn the on- board main antenna towards the Earth in order to increase the signal strength, and used Giotto's telemetry data to check out its instruments.

Considering the pounding undergone by the craft, scientists at the European Space Operations Centre, in Darmstadt, Germany, were pleasantly surprised by the results of their health check, although damage to the thermal blankets and much of the outer shell had produced a marked increase in spacecraft temperature. Sadly, the baffle on the colour camera seemed to have been dislodged, preventing it from sending back any more spectacular images. However, plenty of fuel remained to manoeuvre the craft for a second cometary flyby, and seven of the eleven scientific experiments were still fully or partially operational.

The opportunity was too good to miss. European Space Agency member states were invited to contribute dollars 12m ( pounds 6.3m), in return for which they would be able to take advantage of a rare, low-cost opportunity to study a comet at close quarters. Approval for the attempt was given in June 1991.

Giotto completed another historic first on 2 July 1990 when it passed within 14,500 miles of the Earth and became the first spacecraft to utilise our planet's gravity to change orbit. As a result of this gravitational assist, Giotto was flung towards Comet Grigg- Skjellerup, then returned to hibernation.

The final reawakening came on 7 May 1992. With the aid of the most powerful radio telescopes available - the 70m (230ft) diameter antennae of the American Deep Space Network - contact with Giotto was re-established at a distance of almost 140 million miles.

Despite the loss of the camera system, scientists hope to gain insights into the nature of the dirty snowball and its enveloping coma. The dust impact detection system and the optical probe experiment will measure dust densities, size and distribution. Analysis of the solar wind and the various other charged particles in the coma will be carried out by several instruments, including a plasma analyser provided by the Mullard laboratory, while the magnetometer will study the interaction between the comet and the surrounding environment.

If all goes according to plan, Europe's first interplanetary probe will end its operational life in a blaze of glory as it passes within 300 miles of the comet's nucleus. Giotto's suicide mission will pave the way for an even more ambitious quest soon after the turn of the century: to land on a comet and retrieve a sample for analysis back on Earth.

(Photograph omitted)

Suggested Topics
PROMOTED VIDEO
Life and Style
fashionHealth concerns and 'pornified' perceptions have made women more conscious at the beach
Arts and Entertainment
tv
Sport
Ojo Onaolapo celebrates winning the bronze medal
commonwealth games
Arts and Entertainment
Rock band Led Zeppelin in the early 1970s
musicLed Zeppelin to release alternative Stairway To Heaven after 43 years
Arts and Entertainment
High-flyer: Chris Pratt in 'Guardians of the Galaxy'
filmHe was homeless in Hawaii when he got his big break. Now the comic actor Chris Pratt is Hollywood's new favourite action star
Sport
Van Gaal said that his challenge in taking over Bobby Robson's Barcelona team in 1993 has been easier than the task of resurrecting the current United side
footballA colourful discussion on tactics, the merits of the English footballer and rebuilding Manchester United
Life and Style
Sainsbury's could roll the lorries out across its whole fleet if they are successful
tech
News
ebookA unique anthology of reporting and analysis of a crucial period of history
Travel
The shipping news: a typical Snoozebox construction
travelSpending the night in a shipping container doesn't sound appealing, but mobile crash pads are popping up at the summer's biggest events
Arts and Entertainment
'Old Fashioned' will be a different kind of love story to '50 Shades'
film
Arts and Entertainment
Tracey Emin's 'My Bed' is returning to the Tate more than 15 years after it first caused shockwaves at the gallery
artTracey Emin's bed returns to the Tate after record sale
Arts and Entertainment
Smart mover: Peter Bazalgette
filmHow live cinema screenings can boost arts audiences
Environment
Neil Young performing at Hyde Park, London, earlier this month
environment
Independent
Travel Shop
the manor
Up to 70% off luxury travel
on city breaks Find out more
santorini
Up to 70% off luxury travel
on chic beach resorts Find out more
sardina foodie
Up to 70% off luxury travel
on country retreats Find out more
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Project Coordinator

Competitive: The Green Recruitment Company: The Organisation: The Green Recrui...

Project Manager (HR)- Bristol - Upto £400 p/day

£350 - £400 per annum + competitive: Orgtel: Project Manager (specializing in ...

Embedded Linux Engineer

£40000 - £50000 per annum + competitive: Progressive Recruitment: Embedded Sof...

Senior Hardware Design Engineer - Broadcast

£50000 - £65000 per annum + Benefits: Progressive Recruitment: Working for a m...

Day In a Page

Save the tiger: The animals bred for bones on China’s tiger farms

The animals bred for bones on China’s tiger farms

The big cats kept in captivity to perform for paying audiences and then, when dead, their bodies used to fortify wine
A former custard factory, a Midlands bog and a Leeds cemetery all included in top 50 hidden spots in the UK

A former custard factory, a Midlands bog and a Leeds cemetery

Introducing the top 50 hidden spots in Britain
Ebola epidemic: Plagued by fear

Ebola epidemic: Plagued by fear

How a disease that has claimed fewer than 2,000 victims in its history has earned a place in the darkest corner of the public's imagination
Chris Pratt: From 'Parks and Recreation' to 'Guardians of the Galaxy'

From 'Parks and Recreation' to 'Guardians of the Galaxy'

He was homeless in Hawaii when he got his big break. Now the comic actor Chris Pratt is Hollywood's new favourite action star
How live cinema screenings can boost arts audiences

How live cinema screenings can boost arts audiences

Broadcasting plays and exhibitions to cinemas is a sure-fire box office smash
Shipping container hotels: Pop-up hotels filling a niche

Pop-up hotels filling a niche

Spending the night in a shipping container doesn't sound appealing, but these mobile crash pads are popping up at the summer's biggest events
Native American headdresses are not fashion accessories

Feather dust-up

A Canadian festival has banned Native American headwear. Haven't we been here before?
Boris Johnson's war on diesel

Boris Johnson's war on diesel

11m cars here run on diesel. It's seen as a greener alternative to unleaded petrol. So why is London's mayor on a crusade against the black pump?
5 best waterproof cameras

Splash and flash: 5 best waterproof cameras

Don't let water stop you taking snaps with one of these machines that will take you from the sand to meters deep
Louis van Gaal interview: Manchester United manager discusses tactics and rebuilding after the David Moyes era

Louis van Gaal interview

Manchester United manager discusses tactics and rebuilding after the David Moyes era
Will Gore: The goodwill shown by fans towards Alastair Cook will evaporate rapidly if India win the series

Will Gore: Outside Edge

The goodwill shown by fans towards Alastair Cook will evaporate rapidly if India win the series
The children were playing in the street with toy guns. The air strikes were tragically real

The air strikes were tragically real

The children were playing in the street with toy guns
Boozy, ignorant, intolerant, but very polite – The British, as others see us

Britain as others see us

Boozy, ignorant, intolerant, but very polite
How did our legends really begin?

How did our legends really begin?

Applying the theory of evolution to the world's many mythologies
Watch out: Lambrusco is back on the menu

Lambrusco is back on the menu

Naff Seventies corner-shop staple is this year's Aperol Spritz