Cassini Jupiter Phase C ORS Block 3 Design
Author: Bob West
Tuesday, April 11, 2000
1) Scientific Objectives and observing strategies:
Atmospheric Objectives and strategies:
UVIS: Continuous 10-hr or more map with the slit oriented parallel to the spin axis and
covering both poles to monitor the aurora
ISS: 1X2 mosaic with one image covering the northern hemisphere and one covering the
southern hemisphere.
NIMS: Mapping of Jupiter
CIRS: Longitudinal mapping at two latitudes
Callisto objectives:
NIMS: Opposition phase curve
ISS: Opposition phase curve plus surface detail
UVIS: Opposition phase curve
CIRS: Integrate on Callisto
2) Timeline
Block 3 of Phase C begins at 20 Hrs. UT on day 349 (December 14) 2000. The block
ends at 7 hours, 15 minutes UT on day 350. The block is broken into 6 ‘cyclics’, each
lasting about 2 hours, with the last one cut short by 45 minutes to accommodate a
spacecraft calibration. The phasing should be such that one of them (the next to last) has
ORS instruments taking data 9 minutes before Callisto opposition and ending 1 minute
after Callisto opposition.
Before the cyclic starts orient the spacecraft so that the Z axis is parallel to the spin axis
of Jupiter (takes TBD minutes).
The cyclic looks like this:
a) Integrate on Jupiter for about 30 minutes with boresites targeted to + 30 degrees
b) Do a 1X2 mosaic on Jupiter with footprints centered at +30 and –30 degrees. The
percent overlap of GENMOSA can be adjusted to achieve this.
a) Slew to Callisto (about 2.5 degrees = 43.6 mrad = 183 seconds at 21 seconds/5 mrad),
center Callisto on CIRS FP4. UVIS can accommodate that with FUV Low Res slit.
Allow 30 s for settling time
b) Point at Callisto for 10 minutes, VIMS maps plus ISS images + UVIS + CIRS
spectra
c) Slew back to Jupiter (183 s)
d) Wait 30 s for settling
e) Another 1X2 mosaic one hour after the previous one.
f) Spend the remaining part of two hours integrating with UVIS and CIRS
Cyclic number 1 has the following pointing profile:
20:00 UT Point center of the ISS NAC camera to latitude +30 degrees on the subspacecraft meridian and turn the spacecraft around the Y axis until the Z axis is parallel
to the spin axis of Jupiter. The orientation must be in the sense that the CIRS and VIMS
radiators are pointed in the hemisphere away from the sun
20:30 start the first footprint of the ISS/VIMS 1X2 mosaic (no change in pointing)
20:36: slew the NAC camera to latitude –30 and start the second footprint of the mosaic.
20:45: slew to Callisto, center the CIRS FP4 on Callisto.
21:00 slew back to Jupiter, NAC FOV centered on +30 latitude
21:30 start first footprint of ISS/VIMS 1X2 mosaic (no change in pointing)
21:36 slew to –30 latitude (second ISS/VIMS footprint of 1X2 mosaic).
21:41 remain pointed at latitude –30 and integrate for 19 minutes
Cyclic number 2 begins at 22:00 UT and follows the same pattern except that no time is
needed to orient the Z axis parallel to the spin axis since it will already be in that
orientation.
These repeat up to cyclic number 6. Since the final 45 minutes of cyclic number 6 are
missing, do the last 1X2 mosaic immediately after the last Callisto pointing.
Note, the times may need to be adjusted a little to give 10-minutes integration time on
Callisto in each cyclic. In the example above it is assumed that slewing and settling time
plus ten minutes for observing Callisto total 15 minutes. If more is required start the
Callisto part earlier.
3) Data volume estimates:
Atmospheric science
Mbits
Per 2-hour sub-block
UVIS
VIMS
ISS
CIRS
Total
Total for 12 hours
31
15
64
25
186
90
384
150
810
0.6
15.6
27
2.4
3.6
94
162
14.4
274
Callisto objectives
UVIS
VIMS
ISS
CIRS
Total
Notes:
J. Pearl would like to bias the pointing so that Callisto is centered on CIRS FP4.
Derivation of data volume:
UVIS: Atmospheric data collected at 5 Kbits/second, Callisto at 1 Kbit/s
VIMS: From K Baines, 7.2 Mbits per global map, two maps per 2-hour sub-block
From B. Buratti: 94 Mbits needed for 60 minutes integration on Callisto
ISS: Atmosphere- 32 Mbit per 7-image 2X1 mosaic, 2 mosaics per 2-hour sub-block
ISS Callisto: 14 images per 10 minutes, 1.7 Mbit per image
CIRS Atmosphere: 4 kbit/s on Jupiter, 4 Kbit/s on Callisto
4) Data volume cuts:
TEAM
MBITS
Percent Cut(%) Cut (Mbits)
ALLOCATED
allocated
CDA
CAPS
MIMI
MAG
RPWS
CIRS
ISS
UVIS
VIMS
82
246
236
11
445
81
546
172
128
4.2%
12.6%
12.1%
0.6%
22.9%
4.2%
28.0%
8.8%
6.6%
5.0
0.0
14.1
0.0
26.1
5.0
32.3
10.0
7.5
2.8
0.0
7.9
0.0
14.6
2.8
18.1
5.6
4.2