# What happens to satellites over a million years

I am curious to know what will happen to an average satellite over a 1 million year time span.

Firstly, how high does the perigee need to be in order to not deorbit due to atmospheric friction during that time frame, and is it likely or unlikely that other large bodies eventually perturb the satellite so that it leaves orbit (burns up or escapes is irrelevant).

what effects will radiation pressure and solar wind (1-6x10^-9N/m^2) have on an average satellite (about 3000kg?) Can the satellite be pushed out of orbit?

How much erosion might occur to the satellite due to micro impacts and solar wind impacting on it etc.

• You neglected to mention light pressure, which can be about 1000x greater than the solar wind pressure: en.m.wikipedia.org/wiki/Radiation_pressure
– Yakk
Jan 10 '17 at 11:10
• @yakk ok, added that Jan 10 '17 at 11:19
• The effect of radiation pressure and solar wind does not depend on satellites mass alone, the area is important too.
– Uwe
Jan 10 '17 at 11:40
• How about a cube, or a squat cylinder. With shiny solar panels. Or pick an existing satellite an an example Jan 10 '17 at 13:01
• Jan 10 '17 at 15:38

This is an interesting question to ask but unfortunately is one with:

a) a complex answer requiring much study to explore the variables and

b) many different regimes according to altitude and the various perturbations that apply

A million years is a long time, perhaps a lot comes down to how much of an orbit disturbance is significant to you over that time. I don't wish to put you off but this could be several weeks study with a good orbit propagator. My first reaction would have been to ask for more information on the candidate orbit you have in mind but, realistically this is not going to help in the millions of years time frame because, I believe, this problem is intractable through integration errors. Consider that each of the disposal zones for satellites (LEO - de-orbit, MEO and GEO to local graveyard) has been the subject of stability assessments, i.e. funded studies, that are specific to the satellites in question even over the much shorter periods of a few tens of decades.

Your three tonne suggestion may have nothing like the very specialised characteristics of the 60cm, highly reflective, low area to mass LAGEOS satellites which are at almost 6000km. Even for these most favourable conditions I'd be surprised if the 8 million year estimate is anything better than an order of magnitude.

Over long periods all sorts of inter-relationships between lunar/solar/Earth precession topics come in to play at different timescales. My hazy recollection is that what might be considered to be a stable orbit over decades might not stay that way over hundreds of years.

Short of that effort, from memory and in the immediate timescale:

• solar radiation pressure begins to dominate over atmospheric drag beyond 1000km - 2000km.
• a tumbling object will behave differently to an inertially stable or Earth pointing mission.
• objects in a high Earth orbit with a large Area to Mass ratio, e.g. extended solar arrays, will adopt an increased eccentricity from solar radiation pressure.

These are plausibly hand-calculation territory for a few years. After that you are going to have to bite the bullet and do some serious simulations yourself and at some point in that process you will have to recognise where the uncertainties dominate over the result.

For the slightly longer term: - the Sun's effect on the atmosphere can't be relied upon as a constant, consider the Maunder sunspot minimum.

As far as the effects of the environment on the satellite itself it is not unreasonable to expect an increase in thermal absorption from outgassing, atomic oxygen at LEO, UV and micrometeoroids in that order. Whether that is sufficient to cause any structural damage would be down to the details of design.

Still, its an interesting topic, I'd be happy to hear comments and corrections.

• The question could be more focussed I guess, I am most interested in what it takes to remain in orbit for over 1000000 years, and whether these criteria are the norm or an exception for satellites above LEO. The orbital elements are not interesting, just whether it holds any orbit or not, with bonus interest for naked-eye observable satellites which are still around by then. Jan 11 '17 at 6:43