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ACE Spin/Phase and Sunpulse Information
The ACE spacecraft coordinate system is documented in the ACE Spacecraft Paper, in the ACE Book. An online PDF version is available.
The Z-axis is the spin-axis, with positive pointing toward the Sun. See page 262 of the paper.
A possibly-useful document for visualizing this is online.
So, the X-axis of the -X-Y sun-sensors (also known as the sunpulse-line) is +225 degrees from the official X-axis of the spacecraft. One should be aware that the MAG team uses the sunpulse-line as the X-axis of the spacecraft, a cause of some confusion between them and the SWEPAM team (many years ago).
More info on the sun sensors is in sections 5.11 and 9.3 of the "ACE Spacecraft C&DH Component Spec." It is not online at the ASC currently, because of ITAR restrictions. If you need it, contact the ASC.
The sunpulse-line is spinning around as the spacecraft spins. The sunpulse occurs when the spacecraft-sun line, the sunpulse-line, and the Z-axis of the spacecraft are coplanar (think awhile...)
The Sunpulsetime data are provided in the ACE level 1 data files, in spacecraft clock units (floating-point). Since the spacecraft spins at ~5rpm, these times are ~12 seconds apart. In the ASCII sunpulse files, the sunpulse times are also provied in ACEepoch units (seconds elapsed since 00:00:00 Jan 1 1996), and also in UTC YEAR/Day_of_year.
You may obtain the ACE sunpulse data files here.
Our Email Address: asc@srl.caltech.edu
Last Updated: 23 May, 2013 Return to ASC Home Page