Zarya - Soviet, Russian and International Spaceflight
carousel image
MEV-1 and Intelsat 901

Tyneside, UK
2020 Feb 23
Sunday, Day 54

Maintained by:

Breathing Life Into an Ageing Satellite

2019 October 9, Russia's Khrunichev company launched Northrop Grumman's MEV-1. The Mission Extension Vehicle has been designed to chase down another satellite, dock with it and then take over its steering, pointing and orbit adjustment work. It is a relatively simple task and is a service for the future.

Northrop Grumman is not alone in its approach to spaceborne maintenance. Effective Space Solutions is waiting to get a lift to orbit for a pair of its Space Drone satellites that will perform similar tasks but with extended capabilities including satellite repair using manipulator arms. China, Russia and the US have all been observed conducting missions that hint at using manipulator systems to grapple and release other satellites. The ISS uses manipulator systems to grab and dock visiting spacecraft..

A contract between Intelsat and Northrop Grumman is for MEV-1 to provide its Intelsat 901 satellite with pointing and station-keeping for five years. At that point, the contract could be extended or MEV-1 will move Intelsat to a graveyard orbit and then move itself on to rendezvous and capture of another satellite.

As Things Stand...

...throughout January, everything pointed to MEV-1 and Intelsat 901 meeting in orbit during the final 2-3 days of the month, ready to kick-off proximity operations leading to a docking between them.

Late on January 28 UTC, MEV-1's electric thruster was turned off indicating it had arrived at a point where rendezvous could be initiated. At the time, Intelsat 901 was in a 36,073 km circular orbit. MEV-1 was 225 km higher and in a slightly eccentric orbit, causing it to oscillate between about 500 and 2,000 km from Intelsat. By virtue of its slighly greater orbit period MEV-1 continued slowly to 'catch up' with Intelsat.

Orbit data issued by Space-Track Jan 30 showed MEV-1 again on the move, approaching even closer to Intelsat.

Next moves are awaited.

Diagrams detailing the approach can be found further down this page.


MEV-1 was placed into a 12,000 x 65,000 km, 13°.4 inclined super-synchronous GEO transfer orbit by a Proton rocket along with Eutelsat 5 West B. Once it had been checked out on orbit, MEV-1 started up its low thrust electric engine for near-continuous operation. Its aim was to reach the GEO belt by 2020 February. As of 2020 Jan 29, MEV-1's orbit was close to being geosynchronous.'s launch list for 2019 chronicles the results of its manoeuvres.

Proton-M + Briz-M
Baikonur Cosmodrome, Kazakhstan
2019 Oct 9, 10:17
MEV-1 (Mission Extension Vehicle)
in space
Northrop Grumman spacecraft - planned to rendezvous and attach itself to the Intelsat 901 GEO comsat (28624/2001-024A), stationed at 29° east, and take over its pointing and station-keeping functions in order to extend its on-orbit life by five years. May then move to another satellite. Precise launch time 10:17:56 UTC. Released from the launch vehicle Oct 10 at 02:11 UTC into super-synchronous orbit then pushed towards Intelsat rendezvous by onboard electric thruster system in manoeuvre expected to last about 3.5 months (in preparation, Intelsat 901 departed GEO for graveyard orbit 2019 Dec 11).

epoch (UTC)         
s-m axis
( km )
ecc    perigee
( km )
( km )
( min )
( ° )
( ° )
2019 Oct 10, 15:18448420.590611979649481575.0113.39179
2019 Oct 14, 11:02460210.547914429648571637.579.81179
2019 Nov 22, 20:00454250.386221505565891605.845.20188
2019 Nov 26, 11:14454390.386321510566131606.605.21189
2019 Dec 29, 03:25441860.217228209474071540.592.74207
2020 Jan 03, 05:00441900.217328212474131540.812.75207
2020 Jan 23, 03:30429820.054234272389351478.031.63251
2020 Jan 29, 00:22426670.020835401371751461.811.57266118° west
2020 Jan 31, 17:34424850.003535956362581452.501.56294132° west

Intelsat 901

Intelsat 901 was launched 2011 June 9 by an Ariane 4 flying out of French Guiana. Since 2018 April it had been residing at 29°.5 west longitude in geosynchronous orbit. Prior to that it had been operating at 18° west following a brief period of testing after launch. Orbit measurements are based on Twoline Element Sets published by Space-Track.

Ariane 44L (V-141)
Centre Spatiale Guyanaise, French Guiana
2001 Jun 9, 06:45
Intelsat 901
in space
Commercial comsat.

epoch (UTC)         
s-m axis
( km )
ecc    perigee
( km )
( km )
( min )
( ° )
( ° )
2001 Jun 11, 16:48243440.730518235751630.027.05180
2001 Jun 11, 19:26279240.5089733535757773.993.03178
2001 Jun 12, 18:36381310.103527806356981235.010.62175
2001 Jun 14, 13:41399050.055031332357221322.220.36157
2001 Jun 16, 04:47421380.001035717358021434.710.1325070° west
2001 Jun 19, 04:16421310.001235703358041434.390.1524368° west
2001 Jun 23, 03:26421630.000035784357871436.030.1420967° west
2001 Oct 17, 14:23420380.000035660356611429.640.032843° west
2001 Nov 02, 19:34421070.001635662357971433.170.0129718° west
2001 Nov 04, 13:31421640.000435770358021436.070.017118° west
2018 Mar 25, 05:37421650.000235776357961436.090.0632318° west
2018 Mar 29, 09:48421990.000335809358331437.870.0727920° west
2018 Apr 21, 20:56421630.000335772357981436.010.1221729° west
2019 Dec 01, 20:24421650.000235779357951436.101.448829° west
2019 Dec 14, 09:53421960.000135814358221437.711.4713631° west
2020 Jan 20, 10:34423940.000136010360221447.831.5628893° west
2020 Jan 31, 09:00424600.000136079360851451.221.5886131° west

Starting Point

Initially there was a significant difference in the sizes and inclinations of the two orbits. Intelsat was following a circular orbit around the Earth's equator but MEV-1 was in an inclined and much more eccentric orbit.

The illustrations above and below show the relative locations of the two satellites on 2019 October 9 at noon UTC, the day after MEV-1 reached orbit. The view below shows the fifferences in the shapes of the two orbits.

Orbital Manoeuvres

Following confirmation that MEV-1 had reached space safely and was alive and well, Intelsat began to switch off 901's services and on 2019 Dec 1 its station keeping seemed to come to an end. It started to drift very slowly westwards (<0.2° per day) and increased its inclination slightly from 1°.3 to 1°.45. Commencing December 11, a series of gentle thruster firings were used to push it higher. By January 18 of the new year it was at 35,996 x 36,008 km and still rising although the rate slowed noticeably January 20.

Simultaneously, MEV-1 commenced an operation to lower its orbit to a point where it can be guided to a rendezvous with Intelsat 901. It will latch itself on and its thrusters will be used to return to the geosynchronous belt and guide Intelsat to its new operating slot.

The effects of near-continuous operation of MEV-1's electric thruster system has been to simultaneously raise perigee and lower apogee. At the same time it has been reducing its orbital inclination and moving the Right Ascension of the orbit Ascending Node to match Intelsat's. When both sets of orbital parameters have the same values, it will be in a position to rendezvous with its target and capture it.

By 2020 Jan 18, again at noon, the comparative orbits were distinctly different from those on day one.

Orbit Heights

This plot shows how apogee and perigee of MEV-1's orbit have converged on Intelsat 901. The MEV's target is a 36,000 kilometre circular orbit to match Intelsat. On January 31, the two satellites were matched in orbit height but with a minor difference in orbital eccentricity..

Orbit Inclination

MEV-1 has also slowly been lowering its inclination. It started at 13°.4 but by mid-January the inclination was down to 1°.7, almost matching Intelsat's 1°.4. On January 22, MEV-1's inclination ceased to change and stabilised at 1°.56, probably the desired inclination for the time of rendezvous.

The inclination of the Intelsat orbit was increasing slowly since the time it left its geosynchronous location and, on January 31, it matched MEV-1's 1°.58.

GEO Convergence

The two orbits' values of Right Ascension were also converging. They too fell into alignment on January 31

By mid-January, MEV-1's orbit was dropping into the region that could be considered near-geosynchronous. It was above the western Atlantic Ocean and moving further west. In the meantime, Intelsat was on the equator, in line with the eastern States and also travellig westward. They were converging on a get together in the region of longitude 130° west around the end of January..

Next Moves

Northrop Grumman's engineers may take a few days to prepare for final rendezvous. In response to being questioned about plans, the company indicated a careful approach with an indication that rendezvous and capture will occur "early February". MEV-1 will latch itself on to Intelsat using a grappling device that is designed to connect with the conical nozzle of the thruster used to raise Intelsat 901 from its original transfer orbit.

If all goes well, it will then carry Intelsat 901 to its new geosynchronous operating slot, reportedly 27°.5 west.

Page Date: 2020 Jan 20
Updated: 2020 Jan 23
Updated: 2020 Jan 29
Updated: 2020 Jan 30
Updated: 2020 Jan 31
Chart data: 2020 Feb 1, 00:30 UTC

Copyright © Robert Christy, all rights reserved
Reproduction of this web page or any of its content without permission from is prohibited