Graveyard orbit

Key takeaways

Graveyard orbit belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Graveyard orbit to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Graveyard orbit from memory before moving on to harder problems.

Reference excerpt

A graveyard orbit, also called a junk orbit or disposal orbit, is an orbit that lies away from common operational orbits. One significant graveyard orbit is a supersynchronous orbit well beyond geosynchronous orbit. Some satellites are moved into such orbits at the end of their operational life to reduce the probability of colliding with operational spacecraft and generating space debris.

Overview A graveyard orbit is used when the change in velocity required to perform a de-orbit maneuver is too large. De-orbiting a geostationary satellite requires a delta-v of about 1,500 metres per second (4,900 ft/s), whereas re-orbiting it to a graveyard orbit requires only about 11 metres per second (36 ft/s). For satellites in geostationary orbit and geosynchronous orbits, the graveyard orbit is a few hundred kilometers beyond the operational orbit. The transfer to a graveyard orbit beyond geostationary orbit requires the same amount of fuel as a satellite needs for about three months of stationkeeping. It also requires a reliable attitude control during the transfer maneuver. While most satellite operators plan to perform such a maneuver at the end of their satellites' operational lives, through 2005 only about one-third succeeded. Given the economic value of the positions at geosynchronous altitude, unless premature spacecraft failure precludes it, satellites are moved to a graveyard orbit prior to decommissioning. According to the Inter-Agency Space Debris Coordination Committee (IADC) the minimum recommended perigee altitude Δ H {\displaystyle \Delta {H}} beyond the geostationary orbit is

Δ H = 235 km + C R A [ m 2 ] m [ k g ] ⋅ 1000 km {\displaystyle \Delta {H}=235{\mbox{ km}}+C_{\mathrm {R} }{\frac {A\left[\mathrm {m} ^{2}\right]}{m\left[\mathrm {kg} \right]}}\cdot 1000{\mbox{ km}}}

where

C R {\displaystyle C_{\mathrm {R} }} is the satellite's solar radiation pressure coefficient, whose value is between 1 (for absorption) and 2 (for specular reflection),

A {\displaystyle A} is its aspect area,

m {\displaystyle m} is its mass. This formula includes 200 kilometres (120 mi) for the GEO-protected zone to also permit orbit maneuvers in GEO without interference with the graveyard orbit. Another 35 kilometres (22 mi) of tolerance must be allowed for the effects of gravitational perturbations (primarily solar and lunar). The remaining part of the equation considers the effects of the solar radiation pressure, which depends on the physical parameters of the satellite. In order to obtain a license to provide telecommunications services in the United States, the Federal Communications Commission (FCC) requires all geostationary satellites launched after March 18, 2002, to commit to moving to a graveyard orbit at the end of their operational lives. U.S. government regulations require a boost, Δ H {\displaystyle \Delta {H}} , of about 300 km (186 mi). In 2023 DISH received the first-ever fine by the FCC for failing to de-orbit its EchoStar VII satellite according to the terms of its license. A spacecraft moved to a graveyard orbit will typically be passivated. Uncontrolled objects in a near geostationary [Earth] orbit (GEO) exhibit a 53-year cycle of orbital inclination due to the interaction of the Earth's tilt with the lunar orbit. The orbital inclination varies ± 7.4°, at up to 0.8°pa.

Disposal orbit While the standard geosynchronous satellite graveyard orbit results in an expected orbital lifetime of millions of years, the increasing number of satellites, the launch of microsatellites, and the FCC approval of large megaconstellations of thousands of satellites for launch by 2022 necessitated new approaches for deorbiting to assure earlier removal of the objects once they have reached end-of-life. Contrary to GEO graveyard orbits requiring three months' worth of fuel (delta-V of 11 m/s) to reach, large satellite networks in LEO require orbits that passively decay into the Earth's atmosphere. For example, both OneWeb and SpaceX have committed to the FCC regulatory authorities that decommissioned satellites will decay to a lower orbit – a disposal orbit – where the satellite orbital altitude would decay due to atmospheric drag and then naturally reenter the atmosphere and burn up within one year of end-of-life.

See also List of orbits SNAP-10A – nuclear reactor satellite, remaining in a 700-nautical-mile (1,300 km; 810 mi) sub-synchronous Earth orbit for an expected 4,000 years Spacecraft cemetery, in the Pacific Ocean

Notes

References

Illustrations

Worked examples

Example 1 — a first encounter with Graveyard orbit

Start with the simplest possible case. Write down what Graveyard orbit claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Graveyard orbit before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Graveyard orbit ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Graveyard orbit

In research: Graveyard orbit appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Graveyard orbit in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Graveyard orbit is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astrodynamics, Derelict satellites, Earth orbits, so understanding it makes those chapters shorter.
In everyday life: Look for Graveyard orbit outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Graveyard orbit in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Graveyard orbit means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Graveyard orbit out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Graveyard orbit in simple terms?

A graveyard orbit, also called a junk orbit or disposal orbit, is an orbit that lies away from common operational orbits. One significant graveyard orbit is a supersynchronous orbit well beyond geosynchronous orbit.

Why does Graveyard orbit matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Graveyard orbit?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Graveyard orbit.