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Sustainability in the Space Industry
Published in Mark W. McElroy, The Space Industry of the Future, 2023
Active spacecraft disposal involves two options: either maneuver to a “graveyard” orbit out of harm’s way or intentionally deorbit and burn up in the atmosphere. How does deorbiting work exactly? All orbits decay, but the duration of this process depends on the altitude. At 600 km, an object’s orbit will decay in a few years or months due to atmospheric drag. At 650 km or higher, this process takes longer. Objects in geostationary orbit at 35,000 km will remain there for millions of years. Deorbiting most satellites requires a deliberate end-of-life propulsive maneuver to a different orbit that has a much faster decay rate. An alternative to using a propulsive maneuver is unfurling a tether that slightly increases atmospheric drag and thereby speeds up orbital decay. Spacecraft disposal is not always the only choice. Satellite servicing spacecraft may be used to extend the useful life of existing satellites, thereby eliminating the need to launch and introduce a new replacement spacecraft in orbit [199].
A Place in Space: Marking Emptiness
Published in Jai Galliott, Commercial Space Exploration, 2016
How does a satellite reach and keep its place in the GEO? We know that satellites are launched using shuttles and are undocked in their slots. Using tiny movements to control them, they are placed in their positions and at angles of the right inclination. Though a satellite in its geostationary orbit continues to rotate around the Earth, it tends to wobble and slowly be drawn towards the Earth’s surface little by little (it may take years). This is called orbital decay. If the satellite comes close enough to the Earth, it may re-enter the Earth’s atmosphere and burn up or crash into the surface of the Earth. Orbital decay can be measured and calculated, so tiny rockets are fired regularly to keep the satellites at the right distance from the Earth and maintain its place in the slot for coverage and non-interference from adjoining satellites. The wobbling and orbital decay of satellites becomes a significant form of displacement. As long as the satellite is functioning, the countries are bound to restore the satellites back to their orbits. But once the satellites cease functioning, they are to be placed permanently in a safe high Earth orbit (HEO) according to international regulations. Another kind of place in space is created by HEO called junkyard orbital or ‘graveyard orbit’. Unlike the strict requirements of distances between the satellites in the slots of GEO, the main requirement is that the satellite be moved about 300 kms beyond GEO (Jehn et al. 2005, p. 37).
Smartphone-Based Telemedicine Supported by Pico-Satellite Constellation
Published in IETE Journal of Research, 2019
Omar Ben Bahri, Nissen Lazreg, Kamel Besbes
The pico-satellites in LEO have disadvantages relative to conventional satellites. A pico-satellite has a shorter working life, reduced hardware-carrying capacity, lower transmitter output power capability, and more rapid orbital decay (Table 4).