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Parabolic Arc's Mission Extension Vehicle Headed for Space discusses Northrop Grumman's Mission Extension Vehicle, which is only briefly described in Wikipedia.

The article states:

A satellite launched into space can only bring so much fuel with it, and many times the fuel runs out before the satellite’s components stop functioning. This is where the MEV comes in. It is designed to locate and connect to a satellite running low on fuel, and provide the attitude control and orbit maintenance.

The MEV can dock with about 80% of satellites currently in a geostationary orbit, even if the satellite was not designed to be serviced, and can operate for about 15 years. That means the spacecraft could attach to one satellite for a few years, undock and then help out other satellites in need.

First, I wonder if "dock" is not really the right word, and perhaps it's more of a grappling effect, but hopefully not like this!

Whatever it is, I'd like to understand how it can be done to "about 80% of satellites currently in a geostationary orbit". Glue? Magic fingers? Magnets?

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uhoh
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    Like MDA SIS, MEV would grab the Apogee Kick Motor (assuming it is retained). This goes back to Orbital Express ASTRO: https://en.wikipedia.org/wiki/File:Orbital_Express_1.jpg artists conception shows 3 'fingers' to grasp the AKM ring. – amI Oct 07 '19 at 04:40
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    Like aml says, they essentially harpoon the engine bell and dock that way. – mothman Oct 07 '19 at 05:09
  • @mothman I stand corrected! Looking at that weird probe shown in OM's answer, it does look like slo-mo harpooning! – uhoh Oct 08 '19 at 03:24
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    So what I thought were 'fingers' are just passive bumpers. – amI Oct 08 '19 at 06:24
  • @uhoh sorry, I have no source other than myself for that info. It's the case. The second sentence/paragraph of Organic Marbles answer is exactly correct. – mothman Oct 09 '19 at 07:38

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There isn't much information publicly available, but the MEV appears to dock to the one component many satellites have in common: the rocket engine nozzle.

An extensible probe from the MEV (on the left) enters the rocket nozzle and (presumably) expands its tip.

enter image description here

Frame from a video on the Space Logistics website, annotation mine.

A line in the fact sheet also mentions being able to hook on to "standard launch adaptors"

Docking mechanisms to interface with standard liquid apogee engines and launch adaptors

Full video below.

Organic Marble
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  • So the MEV would do all thrust and attitude control maneuvers for a satellite being out of fuel? – Uwe Oct 07 '19 at 14:23
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    Apparently, the fact sheet (https://www.northropgrumman.com/Capabilities/SpaceLogistics/Documents/MEV_Factsheet.pdf) says " Once docked, the MEV will take over the attitude and orbit maintenance of the combined vehicle stack to meet the pointing and station keeping needs of the customer." – Organic Marble Oct 07 '19 at 14:29
  • I wonder how a satellite not designed for being docked by a MEV behaves friendly to overtaking control by the MEV, especially if there is a little fuel left. Two different attitude controls fighting each other would waste MEV fuel. – Uwe Oct 07 '19 at 14:37
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    Agreed, they'd likely have to shut down the original attitude control system. The MEV must have a highly configurable attitude control system! – Organic Marble Oct 07 '19 at 14:56
  • What about the solar panels of the satellite and the MEV? Both sets of panels should be aligned to the Sun without shadowing each other. If the satellite is able to rotate the panels for alignment, the MEV should be able to do the same. Docking should align both sets of panels for proper simultaneous operation without shadowing. – Uwe Oct 07 '19 at 15:00
  • All I know about the MEV is what was in that fact sheet. I hope more information becomes available, it's a very interesting idea. – Organic Marble Oct 07 '19 at 15:01
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    I don't know how this would work unless the sat. being captured was able to maintain a stable attitude during capture. Capturing a tumbling satellite seems really, really difficult. – Wayne Conrad Oct 07 '19 at 15:21
  • @WayneConrad that's a good point. Luckily they call it the Mission Extension Vehicle rather than The Reanimator ;-) – uhoh Oct 08 '19 at 03:21
  • Depending on the size of the docked to sat you won't have 6 dof attitude control because the cg your rotating outside the control box. Solar panels aren't a freat concern because mev can dock in 360 deg to avoid axial or radial solar – mothman Oct 08 '19 at 04:54
  • More info on MEV mission, including solar panel orientation: https://www.nasaspaceflight.com/2019/10/proton-rocket-launch-northrop-extension-vehicle/ – Hobbes Oct 09 '19 at 08:20
  • Looks like it worked. http://www.parabolicarc.com/2020/02/26/northrop-grumman-successfully-completes-historic-first-docking-of-mission-extension-vehicle-with-intelsat-901-satellite/ – Organic Marble Feb 26 '20 at 23:33