ISS and Hubble have vastly different orbits - different altitudes, different inclinations, requiring a massive delta-V to transfer from one to the other. My question is: has anything ever had to perform such a maneuver (not necessarily between ISS and Hubble specifically)? Or has such a requirement never come up, or just never been feasible?

I'm just asking about precedent for a large inclination change while in orbit.


3 Answers 3


I am not sure if you want count this one, but the currently ongoing "last mission of Cassini" involves the spacecraft changing its inclination gradually from 35 to 64 degrees when it goes through the gap between Saturn and the innermost part of the rings.

NASA image Cassini

The manoeuvre is not done propulsively as large inclination changes are expensive, and the probe is almost out of fuel. (Just for the record, changing the inclination of a circular orbit by 23.9 degrees is as expensive as reaching escape velocity.) Instead, multiple fly-bys of the moon Titan is used to alter the orbit.

A similar approach was used for the Ulysses spacecraft that used a fly-by of Jupiter to enter a solar orbit with an inclination of 80.2 degrees to perform observations of the polar regions of the Sun.

I can not recall that any purely propulsional large change of inclination has been performed, but there exists a Russian plan to keep the ISS alive a little longer by moving their segment to a higher inclination.

  • $\begingroup$ What do you mean by "Just for the record, changing the inclination of a circular orbit by 41.7 degrees is as expensive as reaching escape velocity." - a plane change of 41.7 degrees should take a burn of about 70% of the current orbital velocity but is not related to escape velocity. $\endgroup$
    – asdfex
    Jul 2, 2016 at 10:08
  • $\begingroup$ @asdfex ouch, that angle was in radians. As for escape velocity, it is just for cost comparison. $\endgroup$ Jul 2, 2016 at 11:17
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    $\begingroup$ Even more severe is the plane change undertaken by the Ulysses spacecraft. It used Jupiter to go into a polar orbit about the Sun. $\endgroup$ Jul 2, 2016 at 12:15
  • $\begingroup$ @DavidHammen I forgot about that one. I am going to write it into the answer. $\endgroup$ Jul 2, 2016 at 12:29
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    $\begingroup$ I was looking for any cases where it would have been done propulsively, like in low Earth orbit where there's nothing to fly by - basically, any cases where the circumstances justified the high cost in propellant. $\endgroup$
    – Anthony X
    Jul 2, 2016 at 14:05

As noted, propulsive inclination changes are expensive, so planning tends to avoid them. There was at least one unplanned one I know of. It was ~2 degrees, so for some values of "large"...

Early Tracking and Data Relay Satellite (TDRS) were deployed from the shuttle and used the large solid-fueled Inertial Upper Stage (IUS) to move them from low earth orbit to their planned geosynchronous station.

The first one did not go as planned though. A burn-through in the IUS nozzle left the TDRS in a 19,300 x 11,000 nautical mile orbit inclined 2 degrees to the equator and spinning at 180 degrees/second.

An ingenious plan was devised where careful use of the TDRS's small attitude control thrusters (1 pound-force) stabilized the spacecraft and over the long period between 5 April and 29 June corrected the orbital errors including the inclination using 39 separate burns. Even though early in the maneuver a thruster exploded due to being used in a manner it was never designed for.

Reference: Rescue in Space - TDRS Flight 1


Material in the question Would lunar flyby be less costly in delta-v than direct change from ISS's to Hubble's orbit? applies to

I'm just asking about precedent for a large inclination change while in orbit.

in an interesting way:

note: something like this was used to correct the orbit of PAS-22, making it the first commercial spacecraft to reach near-lunar space if I understand the Wikipedia article correctly. It says:

Using on-board propellant and lunar gravity, the orbit's apogee was gradually increased with several manoeuvres at perigee until it flew by the Moon (9) at a distance of 6,200 km from its surface in May 1998, becoming in a sense the first commercial lunar spacecraft. Another lunar fly-by was performed later that month at a distance of 34,300 km to further improve the orbital inclination.

These operations consumed most of the satellite's propellant, but still much less than it would take to remove the inclination without the Moon assist manoeuvres.

(9)Space Daily's Book Reveals How Hughes Saved ComSat In 1997

For reference, here is Figure 2 of US6116545

from US6116545


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