9. On orbit collision avoidance (for LEO)

TUBS LEO MEO

from a low intensity collision in GEO graveyard orbit (bottom)

There are three general classes of orbit that may be suitable for small satellites the geostationary orbit (GSO), the highly elliptical orbit (HEO) and the low Earth orbit (LEO).

3. Little LEO

(e) Deorbiting at end of LEO and GTO mission this includes both lowering the orbit to reduce the satellite lifetime (e.g. to less than 25 years) and immediate re entry.

It utilizes LEO store and forward satellites in polar orbit.

A. Low Earth and highly eccentric orbits 22 31 5

B. Low Earth orbit scientific space programmes

The Celestri LEO system was designed to enable frequency sharing of the Ka band spectrum with GSO and other LEO systems by using satellite diversity.

For that purpose, mainly three modes of operations were developed first a tracking mode of operation to measure selected objects in low Earth orbit, in geosynchronous orbit and in geostationary transfer orbit.

(e) Deorbit at end of mission this includes both lowering the orbit to reduce lifetime (below 25 years) and immediate re entry.

D. International low Earth orbit communication satellite programmes

2.2.2 Collision risk assessments in low Earth orbit

The M Star system had 72 operational LEO satellites in 12 inclined orbital planes.

Models have predicted that the orbital debris environment could exceed the meteoroid environment in certain regions of low Earth orbit.

The minimum diameter of observable objects was about 10 centimetres for LEO and 1 metre for geostationary satellite orbit (GSO).

The model is applicable to altitudes from LEO to GEO, providing environment estimates in the short term.

Some measurement of small debris in LEO have been done using optical telescopes, but in general, radars outperform telescopes for measurements in LEO.

Preservation of the environment of Low Earth Orbit (LEO) is also important because of its usefulness for various missions such as Earth observation and satellite communication.

Some optical measurements of small debris in LEO have been done, but in general radars outperform telescopes for measurements in LEO.

Research on and development of small, low Earth orbiting satellite communication systems

(e) Post mission disposal of spacecraft from low Earth orbit (LEO).

In the case of higher orbits and if the re entry risk is allowable, the most feasible measure to avoid collision risk with other operating space systems is to reduce the orbital lifetime by reducing the perigee height of the orbit.

It consists of two pairs of satellites, one known as quot eccentric quot , inserted in a high apogee orbit (200,000 km) and the other known as quot auroral quot , inserted in a lower apogee orbit (20,000 km).

In the United States, four groups of such satellites are deployed, namely, communications intelligence (COMINT) in the geostationary orbit (GSO) and signals or electronic intelligence (ELINT) satellites in the GSO and in high elliptical Earth (HEO) and low Earth (LEO) orbits.

It can be reached by propulsive lowering of the perigees of orbits or by propulsive de orbiting.

The Republic of Korea s space programmes include both low Earth orbit (LEO) scientific mission satellite development and geostationary orbit (GEO) communication satellite programmes.

For some satellites on long lifetime LEO orbits, a transfer to shorter lifetime orbits is planned at the end of their activelife.

2.2.2 Collision risk assessments in low Earth orbit 80 85 21

IADC has suggested an algorithm for the determination of the minimum altitude of the disposal orbit above GEO.

For that, mainly three modes of operation were developed a tracking mode of operation to measure selected objects in low Earth orbits (LEO), in geosynchronous orbits (GSO), and in geostationary transfer orbits (GTO).

(a) Research on and development of small, low Earth orbiting satellite communication systems

(c) The accelerated advent of new infrastructures such as low earth orbiting satellite systems (LEOS)

A total of 26 remote sensing satellites will be launched into low altitude, sun synchronous and circular orbits together with 12 (6 in orbit spares) data relay satellites in geostationary orbit.

The influence of low Earth orbit satellite communication systems on the growth of debris in orbit has been investigated in a series of studies.R. Walker, R. Crowther, G. G. Swinerd, The Long Term Implications of Operating Satellite Constellations in the Low Earth Orbit Debris Environment, Advances in Space Research, vol. 19, No. 2, p. 355 358, 1997.

MELEO The Materials Exposure in Low Earth Orbit (MELEO) was an active experiment flown on Shuttle mission STS 52 in October 1992.

In general, lowering the perigee of the orbit, so that the orbital life is 25 years or less, is adequate to protect the future environment.

The minimum size of detectable objects would be 2 6 centimetres in LEO and 20 40 centimetres in GSO.

The Subcommittee noted that by gradually introducing low and medium orbit mobile communication systems, new orbital resources were being exploited, thus reducing future demand on geostationary orbital slots.

In particular, no information is available in the regions of highest density of space debris in LEO (at an altitude of about 800 1000 kilometres) as well as in the geostationary orbit.

(b) Teledesic a low earth orbit system with a constellation of 840 satellites in a Sun synchronous orbit at an altitude of 740 kilometres

In particular, no information is available in the regions of highest density of space debris in LEO (at an altitude of about 800 1,000 km) as well as in geostationary orbit.

Disposal of spacecraft from LEO after their mission.

(e) New uses of space (e.g. commercial LEO communications satellite constellations).