Hi David,

Hmmm... not a situation I'd considered, unfortunately. When I wrote
Integrat, I asked Gareth Williams of the Minor Planet Center if I could
rely on all perturbed orbits in MPCORB.DAT to be of identical epoch. He
replied that yes, this is always the case.

That simplified matters for me. I wrote code that assumed the orbits
could always be integrated from date A to date B, with all of them
starting on A and ending at B. That sped matters up immensely; the
program computes planetary positions _once_, for a grid of dates
between A and B, and then can ignore that part of the puzzle.

Best I can suggest is this. Download the update file, and
integrate it to whatever date you want. Integrate your "current"
MPCORB.DAT file to the same date. _Then_ use the update file to
update your MPCORB.DAT file.

-- Bill