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nyx-space / anise

ANISE provides a toolkit and files for Attitude, Navigation, Instrument, Spacecraft, and Ephemeris data. It's a modern replacement of the NAIF SPICE toolkit.

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Small velocity errors in light time correction and stellar aberration

ChristopherRabotin opened this issue · comments

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Bug report

Describe the bug

In the de440s_translation_verif_aberrations test, it's clear that the velocity computation has a difference on the other of a few millimeters per second compared to SPICE. This is surprising given that it's the same algorithm and that the position error is down to machine precision (so 2e-16 km or 0.2 picometers).

The SPICE code indicates that only the position is corrected for, and not the velocity. However, correcting the velocity in the loop brings the error down to 5 mm/s from 7 mm/s.

To Reproduce

Look at test de440s_translation_verif_aberrations in commit 90b6f40.

Expected behavior

Error should be five orders of magnitude less than it currently is: SPK geometric query error is machine precision in position and 5 micrometers per second in velocity.

Platform

Linux

Additional context

Add any other context about the problem here.