On 22 Mar 2004, "Jorge R. Frank" wrote:

"JimO" wrote in
:

I recall that the higher HST orbit does introduce some vulnerability
to prop failures/leaks that lose you de-orbit sooner than you'd lose
it from the ISS altitude, right?

I believe so, but I'm not sure (in particular, I'd heard RCS deorbit was
not available as a downmode).

RCS Deorbit isn't necessarily a given from an ISS orbit either and neither
an HST or ISS flight has "propellant fail" capability (the ability to
deorbit after the loss of a single OMS propellant tank) once the final
orbit is achieved. Both of these capabilities might exist early in the
mission while still in a lower orbit while the orbiter is still catching up
with the target while deorbit costs are low and propellant reserves are
high, but once rendezvous altitude is achieved there isn't enough
propellant left over to cover either of these failures.

--
Dean Lenort