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A GROUP of Russian and Canadian explorers crossed over the North Pole
on skis last year. Needing precise information about their location, they
carried small emergency beacons like those found on lifeboats. From the
signals these beacons gave out, weather satellites could calculate the skiers’
position. But somehow the skiers, who obviously wanted to carry as little
equipment as possible, had to get this information. A small satellite, built
by the University of Surrey and called UoSAT 2, relayed a message via a
synthetic voice from its computer to the skiers’ hand-held radios every
time that the satellite passed over the pole.

The team at the University of Surrey that builds these ‘smallsats’ is
one of the most successful in the world. Smallsats, also known as ‘lightsats’
or ‘cheapsats’, cost less than a million pounds, compared with the tens
of millions spent on large communications and scientific satellites. The
smallsats can weigh less than 50 kilograms and rarely weigh more than 250
kilograms. The structural parts of such satellites are generally small enough
for a university workshop to manufacture. The satellites are small enough
to fit through normal doors or travel as a ‘passenger’ on airlines, cutting
the cost of providing special facilities. The satellites contain electronic
components bought off-the-shelf rather than the expensive, specially manufactured
electronics that the conventional space industry buys. And the small teams
building smallsats generate far fewer documents and spend far less time
in meetings, cutting costs even further.

Besides being cheaper, smallsats can be put together very quickly to
take advantage of sudden launch opportunities. They can investigate new
phenomena at short notice. Some of the larger space projects take decades
to materialise. The UoSAT-2 satellite, built by the Spacecraft Engineering
Research Unit at the University of Surrey, was launched less than six months
after the decision to build it. (One scientist I spoke to at the British
Antarctic Survey complained that the instrument he was proposing for the
Polar Platform, part of the space station project, would not fly for seven
years, yet it could easily be carried much sooner on a smaller vehicle.)
All of these factors add up to cheaper satellites. The lower financial risk
means that smallsat builders are willing to try out new technologies on
their spacecraft. For example, radio amateurs built the first satellite
to carry integrated circuits made from a complementary metal oxide semiconductor
(CMOS).

Later this year, one of two new satellites being built by the University
of Surrey will carry the first transputers into space (Technology, ¿ìè¶ÌÊÓƵ,
15 April). The transputer is a computer chip that operates very quickly
and allows parallel processing. As well as returning data on their own performance
in space (cosmic radiation can cause errors in a chip’s delicate circuitry),
the transputers will carry out some of the spacecraft’s computational tasks.
Even British government circles have expressed an interest in flying a smallsat
to demonstrate new technologies, and the Royal Aircraft Establishment at
Farnborough is looking at possible designs for such a spacecraft.

Perhaps the biggest advantage of a smallsat is that it is easier to
launch, using a far smaller (and so cheaper) rocket. Anticipating the demand
for smallsat launches, several manufacturers are at work developing and
producing such launchers. There is even a British interest in this field.
A European consortium headed by General Technology Systems in Britain and
including Royal Ordnance is developing a rocket called Little Leo, which
will launch small satellites into low-Earth orbit. The rocket should be
ready for launch in 1992.

Several groups in the US are also developing small launchers. At a conference
on small satellites at Utah State University last year, many people showed
a particular interest in a solid-rocket booster called Pegasus. This rocket
is to be launched at high speed and altitude from under the wing of a B-52
bomber, giving great flexibility as to when and where the satellite can
be launched. Also, the ‘leg-up’ given by the air launch, added to the lift
provided by the wing, means that Pegasus can carry 30 per cent more weight
up to orbit than a rocket of similar size launched from the ground.

So far, though, the most frequent route to space for smallsats is riding
piggyback on one of the large rockets carrying an expensive satellite to
space. Frequently, a launcher’s main cargo does not take the rocket’s full
capacity, so the rocket carries ballast. A small spacecraft can often squeeze
into the spare space, and the launch authority will only charge a few hundred
thousand pounds. It would cost a few million pounds to launch a smallsat
on a small rocket.

Space flights have a hundred or more kilograms of spare capacity so
often that Arianespace has designed a special structure to carry small satellites
as hitchhikers. This structure will make its first flight this summer when
an Ariane 4 rocket will carry six smallsats as well as its main payload,
the SPOT-2 Earth observation satellite. Small satellites have been deployed
from the US’s space shuttle, and, two, built by students at the Moscow Aviation
Institute, were launched by hand from the airlock of the space station Salyut
7.

Another approach is to build a satellite around parts of the rocket
structure that are carried into orbit. Britain participated in the multinational
AMPTE (Active Magnetospheric Particle Tracer Explorer) mission by building
the satellite around a metal ring which separated the two other spacecraft
from West Germany and the US. Britain’s contribution to AMPTE was known
as UKS. Kim Ward, the project manager of UKS, says: ‘The UKS was an example
of an adaptor cone (between the two spacecraft) being transformed into a
highly sophisticated spacecraft able to support a world-class scientific
mission at minimal cost. The spacecraft had many advanced technical features
and during its seven-month lifetime returned vast quantities of unique scientific
»å²¹³Ù²¹.’

Scientific instruments are a common payload for smallsats. A group in
the US has proposed spending $10 million to develop a smallsat, weighing
75 kilograms, to orbit the Moon, taking photographs of the surface. The
photographs would have a resolution 100 times as good as existing maps.

Martin Sweeting, director of the Spacecraft Engineering Research Unit
at the University of Surrey, believes that smallsats have come of age, as
shown by special meetings on the subject organised by, for example, the
European Space Agency. Sweeting adds that smallsats will complement rather
than replace existing spacecraft.

Smallsats will certainly not replace the large communications satellites
that relay telephone calls and television programmes, but they are ideal
for another form of communications known as store-and-forward. In this technique,
a message is sent up to the satellite as it flies overhead. The satellite,
acting as an ‘orbiting post office’, stores the telex-like message until
it passes over the destination, then transmits it to Earth. A satellite
that orbits over the poles passes over every point of the Earth’s surface
at least twice a day. Its orbit takes about 90 minutes, and the Earth turns
20 degrees during each pass of the satellite. So within hours information
can pass from one point on the Earth to another.

Satellites in polar orbits are much closer to the Earth than the geostationary
communications satellites, which need to be at an altitude of 36 000 kilometres
to do their job. So a smallsat in polar orbit needs less power to transmit
its message to Earth. And the equipment needed to receive its signals (a
computer, radio and antenna) will fit into a briefcase.

Although store-and-forward will not replace current instantaneous satellite
communication, the potential applications are numerous. The environmental
group Greenpeace, which runs a research station in the Antarctic, is experimenting
with the store-and-forward equipment on UoSAT-2. Until now, Greenpeace’s
scientists had to wait for suitable weather conditions to allow them to
communicate with the outside world by shortwave radio. For urgent messages
they communicate via an expensive Inmarsat terminal. Suitably equipped smallsats
can interrogate seismological, meteorological and oceanographic sensors
placed in remote areas. Sweeting says that store-and-forward is the only
way in which one satellite can provide global communications.

Smallsats could also have a role in remote sensing. Modern electronic
cameras are compact and reliable enough to fit on them. Although the optics
required for high-quality images are too bulky for smallsats, they can still
produce pictures as good as those from weather satellites.

A rarely recognised but vital application for smallsats is in education.
Many schools and colleges around the world have realised that building and
developing smallsats is the only way that students will get practical experience
of the space industry. One satellite, ORION, designed by the US Naval Postgraduate
School, formed the basis for more than 100 masters’ theses, without even
flying. The equipment needed to receive data from the UoSAT satellites is
cheaply and readily available, and more than 1000 schools and enthusiasts
have received data from them.

Military planners are now taking an interest too. Last year, the US’s
Defense Advanced Research Projects Agency spent $35 million on its version
of smallsats, known as Lightsats. The idea is to find an alternative to
the large reconnaissance, navigational and communications satellites that
the military rely on. These satellites are easy targets. A group of smaller
satellites, doing the same job, would be far harder to disable, and much
easier to replace. The comparative ease of launching means that smallsats
can be kept safely on Earth until they are needed. A battlefield commander
could call up a satellite launch, in much the same way as ordering an air
strike. The Pentagon is examining plans for launching test satellites from
rockets and from submarines.

Radio amateurs, however, are the pioneers: they began flying smallsats
in 1961, only four years after Sputnik, the first ever satellite. They started
off with a tiny biscuit-tin affair which transmitted ‘Hi’ in morse until
its batteries ran out. Later satellites (more than 20 have been launched)
involved other countries through the international Amateur Radio Satellite
Corporation. AMSAT, a non-profitmaking organisation, relies on the space
industry for donations of money and hardware.

The first satellite communications between the US and the USSR was made
through one of AMSAT’s satellites. Japan and the Soviet Union have launched
their own amateur radio satellites, and last year another AMSAT satellite
was injected into orbit with a precision envied by commercial operators.

In the next decade, AMSAT hopes to operate its own geostationary spacecraft,
although the project will stretch its resources. Meanwhile, the corporation
is building tiny store-and-forward ‘Microsats’, each a cube whose sides
measure only 23 centimetres. Four of these will be launched on an Ariane
rocket this summer, alongside two new UoSAT satellites. The new UoSAT satellites
will carry equipment for store-and-forward communications, a radiation detector,
a camera for remote sensing, a parallel-processing computer and several
different solar cells.

True to the origins of smallsats, the UoSAT team at the University of
Surrey began life as an amateur-radio group. In the 1970s, the university
established a station which tracked, and later controlled, some of the early
amateur-radio satellites. In 1979, the Surrey team realised that it could
gather the resources to build its own satellite, and began work on UoSAT-1.
NASA launched this satellite for free in 1981. It carried space-radiation
experiments, radio beacons to study propagation of radio waves in the upper
atmosphere, a magnetomoter and an early design of camera for remote sensing
as well as a digitalker, similar to that which the Soviet and Canadian skiers
relied on last year during their trek over the North Pole. UoSAT-2 was launched
in 1985, and carried a space dust detector, instruments to detect electrons
discharged by the aurorae, a digital communications experiment, a camera
for remote sensing and a digitalker.

The university has set up a company, Surrey Satellite Technology, to
market the spin-offs from its satellite projects. At the smallsat conference
in Utah, the Surrey group, despite operating on a budget far smaller than
its American counterparts, was hailed as a model for all. Now, groups around
the world are taking an interest. The Technical University of Berlin is
hoping to train its students in spacecraft engineering by building satellites
every two years. One of the experiments that it plans to fly is a receiver
to locate tags attached to storks, enabling researchers to track them as
they migrate.

Several American universities collaborated to build Nusat (Northern
Utah Satellite). A beachball-sized satellite launched from the shuttle in
1985, Nusat calibrated air-traffic control radars. One of these universities,
Utah State, has a spin-off company, Globesat, which hopes to fly further
satellites, mostly carrying equipment for store-and-forward communications.
Another, Weber State College, is flying a colour camera for remote sensing
on one of the microsats Arianespace is to launch one in the summer. Japan,
too, flies smallsats carrying scientific equipment. In this way, its scientists
can continue some form of space science irrespective of the ups and downs
of NASDA, the country’s space agency.

There are many firms springing up to enter the small satellite business,
but Sweeting says that the smallsat business still has huge potential: ‘Spacecraft
can now be built by countries without an established space industry.’

Ralph Lorenz is a second-year student of aerospace systems engineering
at the University of Southampton. He worked with the UoSAT group during
summer 1988.