June-September 1981:space activities report

NEW WEATHER SATELLITE

NASA's launch of GOES 5 (Geostationary Operational Environmental Satellite 5) on 22 May is another step in updating the system of world-wide weather satellites in equatorial geosynchronous orbits. The Global Atmospheric Research Programme of 1978-79 included the use of five similar vehicles - three GOES, the European Meteosat 1 and the Japanese GMS - to provide comprehensive coverage of the globe. The system provided almost real-time observations of severe weather patterns, thus allowing warnings to be raised in time for threatened areas, and collected vast amounts of data on temperature, humidity, rainfall, etc. from remote unmanned ground and ocean stations.

The main instrument of these earlier GOES (also known as the SMS or Synchronous Meteorological Satellites) was the Visible and Infrared Spin-Scan Radiometer (VISSR). Reflected sunlight, or radiated heat during the night, shows up the differences between water, land and clouds. The advanced version of VISSR was first launched with GOES 4 last September and also allows temperature and water vapour profiles of the atmosphere to be made. The latter is particularly important because water vapour is thought to be vital for absorbing the Sun’s heat in the atmosphere and driving our weather processes.

GOES 5 will settle down at 85° west longtitude to cover North and South America, plus some of the Atlantic. GOES 4 is performing similar services for the western half of the United States and Canada and much of the eastern Pacific Ocean from its position at 135° west above the equator. Hughes Aircraft Company built both the spacecraft and the main instrument, as well as the satellite's Data Collection System instrumentation and its Telemetry, Tracking and Command Sub-system. The Data Collection System collects and relays environmental data back to Earth from more than 1,500 existing remote platforms on land, at sea and carried aloft by balloons and aircraft, while the telemetry subsystem performs a variety of communications functions.

Also included in the spacecraft's instrumentation package is a Space Environmental Monitor which obtains measurements of solar activity, detects solar flares and measures solar wind intensity and the strength and direction of the Earth's magnetic field.

GOES 5 cost about $20 million, and its launch by the 154th Delta vehicle cost an additional $16 million.

Once checked out by NASA, the new spacecraft will be under the control of NOAA's Earth Satellite Service,which will make the imagery and digital data available to users world-wide through its existing distribution network. The sounding data from the main instrument is not yet available operationally. NOAA is working with NASA to determine how the atmospheric temperature and moisture profiles could be provided to operational users such as the US National Weather Service in the late 1980’s.

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‘ SUPER SHUTTLES’ UNDER STUDY

‘Super Shuttles’ which almost match the heavyweight capability of the Saturn V Moon rockets are being studied, writes Gerald L.Borrowman.

The Marshall Space Flight Center has issued a $596,867 contract to Martin Marietta Aerospace Corporation in New Orleans to study options for upgrading the Shuttle.

The Shuttle, intended as a reusable spaceplane, has a 15x60ft bay designed to carry cargoes of up to 65,000 lbs into a low easterly orbit when launched from the Kennedy Space Center. But larger cargoes are possible, depending on what mission requirements NASA sees for the 1990’s.

In the first phase of the 18-month contract, Martin Marietta will study such mission requirements and develop basic designs for four Shuttle derivatives. Detailed analysis of technology required for more promising concepts will be conducted in the second phase. NASA considers this work to be “technology identification" rather than the start of a new vehicle design.

The four basic types of Shuttle variants are:

1. Placing the main engines in a recoverable module below the external tank would take 15,000 lbs of cargo away, but would make the cargo hold 75 ft long and allow return cargoes to be heavier.

2. Liquid rocket boosters using cousins of the main engines would be more powerful than solid boosters and raise the total cargo to 100,000 lbs.

3. The Shuttle orbiter can be replaced with a one-way cargo canister about the size of the Skylab space station and weighing 150,000 lbs. The engines would be in a recoverable module under the ‘can’.

4. Finally, an all-cargo version with liquid rocket boosters to lift total payload of 200,000 lbs into low Earth orbit.

Costs would also be lower. Earlier studies projected the cost per pound of cargo to be as low as 23 per cent that of the regular Shuttle, while the cost per mission drops to about 80 per cent.

Several improvements are already planned or are being considered at Marshall: squeezing more power out of the main engines and solid rocket boosters, shaving weight off the external tank and boosters, using lightweight booster casings, and using a Titan 3 first stage under the tank to provide an extra boost. All told, these may add as mudh as 54,000 lbs to the basic Shuttle's cargo, bringing it up to 119,000 lbs. Added to the Super Shuttle above, they might ultimately increase the maximum cargo to as much as 245,000 lbs, almost matching the heavyweight record of the Saturn V Moon rocket.

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PAYLOAD FOR SECOND SHUTTLE

When Columbia makes her second flight into orbit, this time piloted by Joe Engle and Dick Truly, she will carry the first load of experiments in her cargo bay. STS-1 was mainly a 'get-up-there-and-get-back-down-safely’ mission and carried only monitoring equipment to record data on the Orbiter’s condition and performance.

The payload for STS-1 is OSTA-1, named after NASA’s Office of Space and Terrestrial Applications who provides most of the seven experiments. It is designed to demonstrate the Shuttle’s capability as an operational space platform for scientific and applications research with the experiments primarily looking at remote sensing of land resources,atmospheric phenomena and ocean conditions.

These include an imaging radar (Shuttle Imaging Radar, or SIR-A) to test advanced techniques for mapping geological structures important in oil and gas exploration; a multispectral infrared radiometer (SMIRR) to measure the solar reflectance of mineral-bearing rock formations; a feature recognition system (Feature Identification and Location Experiment, or FILE) designed to discriminate between water, bare ground, vegetation, snow or clouds and thus control sensors to collect desired data; an air pollution measurement experiment (measurement of air pollution from satellites,or MAPS) designed to measure the distribution of carbon monoxide in the middle and upper troposphere (12-18 km or 7.5-11 miles altitude); an ocean colour scanner (Ocean Color Experiment,or OCE) to map algae concentrations which may indicate feeding areas for schools of fish or pinpoint possible pollution problems; a night and day optical survey of lightning storms (NOSL); and a biological engineering experiment (Heflex Bioengineering Test, or HBT) to determine the relationship between plant growth and moisture content in the near-weightlessness of space.

An engineering model of a Spacelab pallet, a 3 m (10 ft) long U-shaped structure mounted in the cargo bay, carries most of the experiments. The pallet is equipped with subsystems to provide power, command, data and thermal interfaces for the instruments. The imaging radar, radiometer, feature recognition,pollution measurement and ocean scanner experiments are mounted on the pallet; the lightning and biological engineering experiments are mounted in the Shuttle’s crew compartment.

STS-2 will be launched from the Kennedy Space Center into a 280 km (174 mi) circular orbit with an inclination of 40.3 degrees. For approximately 3.5 days (88 hours) of the four-day mission, the Shuttle will be in an Earth-viewing orientation where the payload bay faces the Earth on a line perpendicular to the surface. During this period, the instruments will be operated and data collected. The flight operations of OSTA-1 will be controlled from the Johnson Space Center Payload Operation Control Center (POCC) in Houston. The air pollution and feature recognition experiments operate continuously for the whole mission with the imaging radar, radiometer and ocean experiments taking data over preselected sites. The lightning experiment is a ‘target of opportunity’ instrument experiment housekeeping data is available in the Payload Operation Control Center to monitor the status an health of the instruments, and the payload can be commanded from the control centre, or by the astronaut crew via the Shuttle’s general purpose computer. Since most of the Shuttle data transmission capability will be taken up with Shuttle status data this flight all of the OSTA-1 scientific data will be recorded onboard on tape and film.

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ARIANE TO THE PLANETS

A study by the European Space Operation Centre’s Mission Analysis Office has shown that the Ariane III and IV launcher versions, plus a fourth stage, can handle useful payloads to the planets, comets and asteroids.

Ariane IV should be available in the middle of this decade and with a fourth stage it could put 1649 kg into orbit around the Moon. Since Europe is interested in a POLO (Polar Orbiting Lunar Observatory) for making a complete global survey of the Moon's physical and chemical properties this is an important result.

The same launcher combination could send 1950 kg towards Mars where it could slip a vehicle into a circular equatorial orbit near Phobos or Deimos (masses after retromanoeuvres 721 and 672 kg respectively). Ariane III could handle about half of these masses. Smaller velocity changes could then result in a Mars-moon orbiter or lander.

Direct launches to Jupiter and Saturn require higher energies and only fly-by probes are really feasible for Ariane this decade. Even then they are under 400 and 300 kg for Jupiter and Saturn, respectively. However, a 1000 kg craft could be put into orbit about Venus.

A multiple-asteroid mission (Asterex) is being studied by ESA at present for this decade. One quoted example is a five-asteroid fly-by with a vehicle weighing 970 kg before the first encounter.

Comets, of course, will be coming under close scrutiny for the first time when Halley is intercepted in 1986. ESA's Giotto probe will weigh about 750 kg and carry 50 kg of experiments but,by comparison, a 1987 mission to Comet Borelly by Ariane IV/fourth stage could see a 1500 kg probe being used.