I have no idea whether or not there will be further manoeuvres, but there is a precedent. Lacrosse 4 made a small manoeuvre to further circularize its orbit, about 33 h after its first circularization manoeuvre. Unlike the first manoeuvre, the second one was nowhere near Diego Garcia, or any other tracking station I could identify. Lacrosse 5's orbit is about 30 km higher than that of any previous Lacrosse. Perhaps it is intended to maintain some minimum required altitude over a potentially long service life in orbit. I note that Lacrosse 2 has decayed 32 km since it was launched 14 years ago. Lacrosse 5's higher orbit has an effect on its revisit rate with respect to targets on the ground. Previous Lacrosses nearly repeated their ground track every two days (29:2 resonance). Lacrosse 5 will nearly repeat its ground track every three days (43:3 resonance). I have insufficient information at this time to judge which of the above was the primary motivation for the higher orbit. If Lacrosse 5 manoeuvres again, I suspect its mean motion will decrease to between 14.5165 and 14.5232 rev/d. A 14.5165 rev/d orbit would result in an exact 43:3 resonance; however, U.S. optical imagers almost never operate in an exact resonance. The lone exception was Misty 1, which operated in almost exactly a 127:9 and later a 43:3 resonance. I arrived at the 14.5232 rev/d alternative, based on the apparently slightly greater than usual eccentricity of the present orbit - about 0.00086, instead of the more typical 0.0004; increasing the perigee height to achieve 0.0004 eccentricity, would result in a 14.5232 rev/d orbit. Of course, this analysis is based upon the orbit I posted last night, which is based upon a fairly short arc. A manoeuvre to a 14.5165 rev/d orbit would increase the orbital period by about 7 s, causing the satellite to arrive about 100 s late 24 h after a manoeuvre. Ted Molczan ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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