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
peopleTop Gear presenter and all-round controversialist is at it again
Aaron Ramsey celebrates after opening the scoring in Arsenal's win over Hull `
peopleActress speaks out against historic sexual assault claims, saying things have 'gone quite far now'

Arts & Entertainment
A stranger calls: Martin Freeman in ‘Fargo’
tvReview: New 10-part series brims with characters and stories

Life & Style
Guests enjoy food and cocktail parings by Chefs Jimmy Bannos, Jimmy Bannos Jr, Daniel Rose and Mindy Segal with mixologists Josh King and Alex Gara at Bounty & Barrel: A Jack Daniel's Single Barrel Dinner Series at Heaven on Seven on April 9, 2014 in Chicago, Illinois.
food + drinkSprinkle Palcohol 'on almost any dish' for 'an extra kick' firm says...
Coren Mitchell, who is the daughter of the late broadcaster Alan Coren and is married to comedian David Mitchell, produced a hand to make poker history at the 98th EPT main event.
peopleJournalist and TV presenter becomes first ever two-time winner of the European Poker Tour
Arts & Entertainment
Shaun Evans as Endeavour interviews a prisoner as he tries to get to the bottom of a police cover up
tvReview: Second series comes to close with startling tale of police corruption and child abuse
Arts & Entertainment
Schwarzenegger winning Mr. Universe 1969
arts + entsCan you guess the celebrity from these British Pathe News clips?
politicsLabour launches the 'completely hollow' Easter Clegg
Luis Suarez celebrates after scoring in Liverpool's 3-2 win over Norwich
sport Another hurdle is out of the way for Brendan Rodgers' side
Portrait of Queen Elizabeth-II by David Bailey which has been released to mark her 88th birthday
peoplePortrait released to mark monarch's 88th birthday
Arts & Entertainment
The star of the sitcom ‘Miranda’ is hugely popular with mainstream audiences
TVMiranda Hart lined up for ‘Generation Game’ revival
Life & Style
The writer, Gerda Saunders, with her mother, who also suffered with dementia before her death
healthGerda Saunders on the most formidable effect of her dementia
Arts & Entertainment
Last, but by no means least, is Tommy Cooper and the fez. This style of hat became a permanent trademark of his act.
comedyNot Like That, Like This centres on alleged domestic abuse
Arts & Entertainment
Oxegen in Ireland has been axed as promoters decide it is 'no longer viable'
arts + ents Promoters have axed the event as it is 'no longer viable in current form'
Travel Shop
the manor
Up to 70% off luxury travel
on city breaks Find out more
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
Have you tried new the Independent Digital Edition iPad app?
Independent Dating

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

iJobs Job Widget
iJobs General

Geography Teacher

£130 - £140 per day: Randstad Education Ilford: Secondary Geography Teacher Lo...

Do you want to work in Education?

£55 - £70 per day: Randstad Education Cheshire: Are you a dynamic and energeti...

SEN Teaching Assistant

Negotiable: Randstad Education Group: SEN TAs, LSAs and Support Workers needed...

Private Client Senior Manager - Sheffield

£50000 - £60000 per annum: Pro-Recruitment Group: The Sheffield office of this...

Day In a Page

Rubin ‘Hurricane’ Carter: The man who could have been champion of the world - and the Bob Dylan song that immortalised him

The man who could have been champion of the world

Rubin ‘Hurricane’ Carter and the Bob Dylan song that immortalised him
Didn’t she do well?

Didn’t she do well?

Miranda Hart lined up for ‘Generation Game’ revival
The Middle East we must confront in the future will be a Mafiastan ruled by money

The Middle East we must confront in the future will be a Mafiastan ruled by money

In Iraq, mafiosi already run almost the entire oil output of the south of the country
Before they were famous

Before they were famous

Can you guess the celebrity from these British Pathe News clips?
Martin Freeman’s casting in Fargo is genius

Martin Freeman’s casting in Fargo is a stroke of genius

Series is brimming with characters and stories all its own
How I brokered a peace deal with Robert Mugabe: Roy Agyemang reveals the delicate diplomacy needed to get Zimbabwe’s President to sit down with the BBC

How I brokered a peace deal with Robert Mugabe

Roy Agyemang reveals the delicate diplomacy needed to get Zimbabwe’s President to sit down with the BBC
Video of British Muslims dancing to Pharrell Williams's hit Happy attacked as 'sinful'

British Muslims's Happy video attacked as 'sinful'

The four-minute clip by Honesty Policy has had more than 300,000 hits on YouTube
Church of England-raised Michael Williams describes the unexpected joys in learning about his family's Jewish faith

Michael Williams: Do as I do, not as I pray

Church of England-raised Williams describes the unexpected joys in learning about his family's Jewish faith
A History of the First World War in 100 moments: A visit to the Front Line by the Prime Minister's wife

A History of the First World War in 100 moments

A visit to the Front Line by the Prime Minister's wife
Comedian Jenny Collier: 'Sexism I experienced on stand-up circuit should be extinct'

Jenny Collier: 'Sexism on stand-up circuit should be extinct'

The comedian's appearance at a show on the eve of International Women's Day was cancelled because they had "too many women" on the bill
Cannes Film Festival: Ken Loach and Mike Leigh to fight it out for the Palme d'Or

Cannes Film Festival

Ken Loach and Mike Leigh to fight it out for the Palme d'Or
The concept album makes surprise top ten return with neolithic opus from Jethro Tull's Ian Anderson

The concept album makes surprise top ten return

Neolithic opus from Jethro Tull's Ian Anderson is unexpected success
Lichen is the surprise new ingredient on fine-dining menus, thanks to our love of Scandinavian and Indian cuisines

Lichen is surprise new ingredient on fine-dining menus

Emily Jupp discovers how it can give a unique, smoky flavour to our cooking
10 best baking books

10 best baking books

Planning a spot of baking this bank holiday weekend? From old favourites to new releases, here’s ten cookbooks for you
Jury still out on Manchester City boss Manuel Pellegrini

Jury still out on Pellegrini

Draw with Sunderland raises questions over Manchester City manager's ability to motivate and unify his players