EXPLORING THE UNIVERSE
and Mariner 10 made the first rendezvous with the inner
planet Mercury. Next came the missions to the outer plan-
ets, first with Pioneers 10 and 11, and then with the two
Voyagers. Pride of place must go to Voyager 2, which was
launched in 1977 and bypassed all four giants – Jupiter
(1979), Saturn (1981), Uranus (1986) and finally Neptune
(1989). This was possible because the planets were strung
out in a curve, so that the gravity of one could be used to
send Voyager on to a rendezvous with its next target. This
situation will not recur for well over a century, so it came
just at the right moment. The Voyagers and the Pioneers
will never return; they are leaving the Solar System for
ever, and once we lose contact with them we will never
know their fate. (In case any alien civilization finds them,
they carry pictures and identification tapes, though one has
to admit that the chances of their being found do not seemto be very high.) Neither must we forget the ‘armada’ to
Halley’s Comet in 1986, when no less than five separate
satellites were launched in a co-ordinated scientific effort.
The British-built Giotto went right into the comet’s head
and sent back close-range pictures of the icy nucleus.
On 22 September 2001 the probe Deep Space 1
passed the nucleus of Borrelly’s comet at a range of
2120 km (1317 miles), and sent back excellent images.
By 2003 all the planets had been surveyed, apart from
Pluto, as well as numbers of asteroids.
Finance is always a problem, and several very inter-
esting and important missions have had to be postponed
or cancelled, but a great deal has been learned, and we
now know more about our neighbour worlds than would
have seemed possible in October 1957, when the Space
Age began so suddenly. Shuttle launch. In an
outpouring of light visible
hundreds of miles away,
the Space Shuttle Discovery
thunders skywards from
Launch Pad 39B at 01 29h
EDT, 8 April 1993. Aboard for
the second Space Shuttle
mission of 1993 are a crew of
five and the Atmospheric
Laboratory for Applications
and Science 2 (ATLAS 2),
which was to study the
energy output from the Sun
and the chemical
composition of the Earth's
middle atmosphere.▼ The Chandra X-ray
satellite was launched on
23 July 1999. The main
instruments were a CCD
imaging spectrometer and
high-resolution camera; it
was far more sensitive than
any previous X-ray satellite.▼ IUE. The International
Ultra-violet Explorer,
launched on 26 January
1978, operated until 1997,
though its planned life
expectancy was only three
years! It has carried out
a full survey of the sky at
ultra-violet wavelengths,
and has actually provided
material for more research
papers than any other
satellite.B Atl of Univ Phil'03stp 31/3/03 3:58 pm Page 25