SwRI CAPS ICO DOY 004 page
 
CAPS Checkout Report 1999 DOY 004
from the desk of CAPS PI: Dave Young
The first day out of 3 days of CAPS checkout was completed successfully this morning. The data quality throughout the pass was generally very good with minimal to no time lags. Commanding went smoothly, including the creation and radiation of several contingency commands. Parallel operations with MIMI and INMS were accommodated without problems.
The IBS was brought up first. The 3 channeltron detectors operated flawlessly as indicated by the expected level of the noise count rate (~1/sec) once detector high voltages were on. The electrostatic analyzer voltages were checked out successfully, after which IBS was allowed to operate in its solar wind survey mode for 20 minutes. The accompanying data were taken several hours later, following ELS checkout. In the IBS plots, ion energy/charge increases logrithmically from right to left, varying from about 250 eV to 10 keV. IBS has 3 detectors (coded by color) which view in roughly the same direction. The figure shows a weak solar wind-like spectrum of ions taken with the IBS aperture facing roughly in the direction of the Huygens Probe (along the s/c -X axis). Since the fields-of-view of all 3 CAPS sensors are pointed roughly perpendicular to the direction of solar wind flow throughout most of ICO, the origin of these ions is not yet understood but may be caused by scattering off of s/c or Probe surfaces.
After its checkout IBS was commanded off and ELS was brought on. The ELS checkout went smoothly, culminating in observations of photoelectrons (generated by the Cassini s/c) and solar wind electrons. The accompanying figures show superimposed energy spectra from eight different ELS look-directions covering electron angles of arrival from directions near the high gain antenna (EL channels 6-8) to near the s/c +Z (thrust) direction (EL channels 1-3). The prominent dip in the electron spectra near energy channel 54 is thought to divide lower energy photoelectrons from solar wind electrons. Electron energy increases from right to left in the figure and covers the range from ~1 eV through 27 keV. The s/c potential may be inferred from this plot to be about 6.5 volts positive at this time.
Some difficulties were encountered with initial tests of the IMS data processing system (CPU2). Only 50% of the data is received at one time in alternating 32 sec periods. The problem is thought to be caused by a software timing conflict that has been observed and fixed before. The problem is under study in the lab using the CAPS engineering model. It is believed to be correctable with a modification to the flight software. Difficulties were also encountered with the actuator/motor that turns the CAPS field-of-view by up to +/- 104 degrees about the s/c Z-axis. Some temporary sticking of the actuator occurred at the ~ -100 degree point of motion with the motor continuing to drive towards the -104 degree limit. Sticking is apparently caused by the stiffness of the flexible cable that carries CAPS signals from the s/c through the actuator to the DPU. Before a command could be uplinked to turn off the actuator, the system moved freely through its range of motion before being commanded to stop at +90 degrees. The actuator was then commanded back to its neutral position (FOV aligned with the imager boresights)
 
 
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ELS Data from DOY 004, UTC: 14:53:46
ELS DOY 004 Data
ELS Data from DOY 004, UTC: 15:52:58
ELS DOY 004 Data
IBS Data from DOY 004, UTC: 14:14:50
IBS DOY 004 Data
IBS Data from DOY 004, UTC: 15:52:58
IBS DOY 004 Data