049IA – Cassini Iapetus Targeted Flyby (Rev. 049, 10 Sep 2007)
              Planning Web Page

Images can be found --> here

Introduction

The Cassini group of ISS Team member Prof. Gerhard Neukum was responsible for imaging planning of Cassini's targeted flyby at Iapetus on 10 September 2007. We also helped to design the timeline during the SOST Iapetus segment (08 September 2007 21:50 to 12 September 2007 21:35 UTC/SCET), initiated a reference trajectory tweak to significantly improve closest-approach science without sacrificing the UVIS stellar occultation, and designed the spacecraft attitude (trackings, mosaics, pointings) of the VIMS_049IA_ORSHIRES001_PRIME request for all remote-sensing (ORS) and fields-and-particle (MAPS) instruments. This request covers the time frame from 55 min before to 3 hours after closest approach.

The 049IA flyby is the only Iapetus flyby within Cassini's six years long orbit tour. Iapetus is difficult to reach because it is far away from the other satellites, and because it's orbit has a significant inclination. On the other side, with 2.4 km/s or ~9000 km/h relative velocity, the Iapetus flyby is a very slow flyby, giving the scientific instruments much more time to collect data from nearby than at other satellite flybys. This web page describes the ISS planning in great detail.

More general information about the flyby can be found on the web sites from JPL and CICLOPS:

• JPL Press Release 05 Sep 2007
• CICLOPS announcement 05 Sep 2007
• Mission summary (pdf, 2.4 MB)
• Pointing simulation (QuickTime movie, 71.7 MB -- large!)




Timeline

The table shows the observation timeline during the SOST Iapetus segment. Colors indicate the prime instrument (responsible for spacecraft pointing). Format for the start time of a request is Year-"day-of-year" T hh:mm:ss, with 2007-253T = Sep. 10, 2007.

The time window between 08:45 and 20:00 UTC on DOY 253 is designed as a "moveable block". This means that deviations from the reference trajectory can be corrected at very short notice, crucial for a correct instrument pointing near closest approach (C/A). There's a deadtime of ~5 min on either side to accomodate a potential time shift. The epoch is relative to the Iapetus closest approach time which occurs at C/A = 2007-253T14:15:40 UTC/SCET in the reference trajectory. This is equivalent to 16:15 Central European time on Monday, Sep. 10, or 07:15 Pacific Daylight time on same day. Within the moveable block, the waypoint strategy is also not used. Instead, "custom hand-offs" organize the hand-overs of the spacecraft attitudes between the different instrument requests. This allows a much higher flexibility than many turns to and from a waypoint.

Geometry information for closest approach:
Altitude: 1615 km
Sub-S/C lat/lon: 3.4°S/155.4°W
Sub-solat lat/lon: 1.4°N/214.4°W
Phase angle: 58.9°


During custom period, the primary axis (ISS NAC boresight) points towards Iapetus most of the time. An exception is the UVIS star occultation (request ICYEXO009), where the UVIS FUV sensor points towards Sigma Sagitarii (Nunki) for 25 minutes. The secondary axis has been chosen in favor of the MAPS instruments. Between C/A -1:45 hrs and +23 min, the -X axis of Cassini points as close as possible in the direction of spacecraft motion ("S/C ram") relative to Iapetus. Then, the radiators of the ORS instruments would turn into sun, requiring a secondary axis switch. This "big turn" needs 15:44 min. of time and ends at the new secondary orientation "-X to Iapetus north pole".

The request VIMS_049IA_ORSHIRES001_PRIME (C/A -0:55 to +3:00 hrs) will be the one where the most important data will be taken, including images with spatial resolutions down to ~10 m/pxl. It is subdivided into 10 tracking periods, where different parts on the surface are tracked by the Cassini IVP (Inertial Vector Propagator). Tracking of the surface is essential to not getting smeared images. This request also contains the "big turn" described above.

A small fraction of the data will be downlinked to Earth on the late evening of Sept., 10. The majority will follow overnight (US) or during daytimes on Sept., 11 (Europe). Since the Iapetus data have a particularly high priority, all data will either be downlinked twice, or received by two stations simultaneously. The intermediate downlink late on DOY 253 allows to collect about 20% more data during the flyby than would be possible otherwise.





Observation requests: detailed information

Maps with ISS footprints from multiple requests ("summary maps") can be found here:
• Map of ISS coverage and spatial resolution
• All custom period footprints
• First custom period observations until "2901"
• All ISS_049IA_ORSHIRES001_VIMS footprints
• Global mapping at ~400-500 m/pxl
• Regional multi-color coverage
• Moat-crater area coverage in saturnshine
• Saturn occultation by Iapetus (animation)
• Global inbound observations (high phase)
• Global outbound observations (low phase)


Detailed information on specific ISS observations is available here:



Request name	Part	Resolution	Notes and preview diagrams
ISS_049SA_SATSYSFIA001_PRIME	moons	13-7 km/pxl	Hy, Ti, Te, Mi, Rh, En, Di
	WAC	196 km/pxl	Saturn
	rings	20 km/pxl	Rings NAC mosaic
ISS_049IA_M33HRS001_PRIME		1.7 km/pxl	Iapetus crescent 1x1 mosaic
ISS_049IA_GLOBMAPG001_PRIME		1.3 km/pxl	Crescent 1x2
ISS_049IA_LIMBTOPOG001_PRIME		800 m/pxl	Crescent 1x2 + saturnshine
ISS_049IA_SATUSHINE001_PRIME		490 m/pxl	Crescent 1x4
		470 m/pxl	High southern and northern latitudes 1x3 each
		460 m/pxl	Ridge stereo
		450 m/pxl	Landslide crater saturnshine attempt
ISS_049IA_FP1NITMAP001_CIRS		235 m/pxl	Crescent at low southern lat.
ISS_049IA_CASSREG001_PRIME		85 m/pxl	Ridge at 130°W
ISS_049IA_ICYMAP003_UVIS		80 m/pxl	1x3 mosaic at mid northern lat.
ISS_049IA_ICYEXO009_UVIS		450 m/pxl	WAC crescent + star (Nunki)
ISS_049IA_ORSHIRES001_VIMS	2901	30 m/pxl	Ridge (140°W) at high phase
	2902	20 m/pxl	Bright "Voyager" mountains at horizon
	2903	10 m/pxl	Closest approach imaging (phase from 83° to 29°)
	2904	20 m/pxl	Average dark terrain sample (for CIRS)
	2905	60 m/pxl	Transition zone (mid southern latitudes)
	2906	35 m/pxl	Average bright terrain sample (for CIRS)
	2907	50 m/pxl	1x6 mosaic of bright "Voyager" mountains
	2908	60 m/pxl	Average bright terrain sample (for VIMS)
	2909	80-130 m/pxl	4x3 + 3x3 big transition zone mosaic (equatorial)
	2910 +2911	140 m/pxl	Terminator mapping and "moat" crater saturnshine
ISS_049IA_FP1DAYMAP001_CIRS		240 m/pxl	1x3 mosaic at low southern lat.
ISS_049IA_IAPETUS013_VIMS		250 m/pxl	Part of huge trailing-side basin
		260 m/pxl	Equatorial transition zone multi-color
ISS_049IA_REGMAPTRL001_PRIME		440 m/pxl	Hamon crater multi-color; 15 panel trail. side mosaic
		470 m/pxl	"Moat" crater in saturnshine
		500 m/pxl	Latitudinal multi-color coverage
ISS_049IA_REGCOLTRL001_PRIME		610 m/pxl	"Moat" crater in saturnshine
		630 m/pxl	Local multi-color
ISS_049IA_IAPETUS010_VIMS		1.6 km/pxl	Global multi-color trailing side
ISS_049IA_LIMBTOPOI001_PRIME		2.3 km/pxl	Global view





Flyby geometry

This table shows the flyby geometry in 1-hour steps for altitudes below ~100,000 km, in 10-min steps for altitudes below ~10000 km, and in 1 min. steps for altitudes below ~2000 km.

UTC/SCET = Cassini event time; ALTITUDE = distance to surface (in km); SC_LAT/LON = sub-spacecraft latitude/longitude; Sun_LAT/LON = sub-solar latitude/longitude (all longitudes are given in degrees west); PHASE is phase angle (with 0° = fully illuminated, 90° = half moon, 180° = new moon).

UTC/SCET	ALTITUDE	SC_LAT	SC_LON	Sun_LAT	Sun_LON	PHASE
2007 SEP 10 03:00	94381	+9.7	65.1	+1.4	212.3	145.2
2007 SEP 10 04:00	85946	+9.7	65.4	+1.4	212.5	145.0
2007 SEP 10 05:00	77511	+9.7	65.8	+1.4	212.7	144.9
2007 SEP 10 06:00	69075	+9.7	66.2	+1.4	212.9	144.7
2007 SEP 10 07:00	60640	+9.7	66.7	+1.4	213.1	144.4
2007 SEP 10 08:00	52206	+9.7	67.2	+1.4	213.2	144.1
2007 SEP 10 09:00	43774	+9.6	67.9	+1.4	213.4	143.6
2007 SEP 10 10:00	35345	+9.6	68.8	+1.4	213.6	142.9
2007 SEP 10 11:00	26924	+9.5	70.2	+1.4	213.8	141.9
2007 SEP 10 12:00	18522	+9.4	72.5	+1.4	214.0	139.8
2007 SEP 10 13:00	10184	+8.9	78.2	+1.4	214.2	134.6
2007 SEP 10 13:10	8813	+8.7	80.1	+1.4	214.2	132.9
2007 SEP 10 13:20	7455	+8.5	82.6	+1.4	214.2	130.5
2007 SEP 10 13:30	6117	+8.1	86.0	+1.4	214.3	127.3
2007 SEP 10 13:40	4813	+7.5	91.1	+1.4	214.3	122.4
2007 SEP 10 13:50	3578	+6.5	99.1	+1.4	214.3	114.6
2007 SEP 10 14:00	2488	+4.4	112.8	+1.4	214.4	101.2
2007 SEP 10 14:05	2053	+2.5	123.3	+1.4	214.4	90.7
2007 SEP 10 14:06	1980	+2.1	125.8	+1.4	214.4	88.3
2007 SEP 10 14:07	1912	+1.6	128.4	+1.4	214.4	85.7
2007 SEP 10 14:08	1850	+1.1	131.1	+1.4	214.4	83.0
2007 SEP 10 14:09	1795	+0.6	134.0	+1.4	214.4	80.2
2007 SEP 10 14:10	1746	0.0	136.9	+1.4	214.4	77.2
2007 SEP 10 14:11	1704	-0.6	140.0	+1.4	214.4	74.1
2007 SEP 10 14:12	1670	-1.2	143.2	+1.4	214.4	71.0
2007 SEP 10 14:13	1644	-1.8	146.5	+1.4	214.4	67.8
2007 SEP 10 14:14	1626	-2.4	149.8	+1.4	214.4	64.5
2007 SEP 10 14:15	1616	-3.0	153.2	+1.4	214.4	61.1
2007 SEP 10 14:16	1615	-3.6	156.6	+1.4	214.4	57.8
2007 SEP 10 14:17	1622	-4.2	160.0	+1.4	214.4	54.5
2007 SEP 10 14:18	1638	-4.8	163.3	+1.4	214.4	51.3
2007 SEP 10 14:19	1662	-5.3	166.7	+1.4	214.4	48.1
2007 SEP 10 14:20	1693	-5.8	169.9	+1.4	214.4	44.9
2007 SEP 10 14:21	1733	-6.3	173.1	+1.4	214.4	41.9
2007 SEP 10 14:22	1779	-6.8	176.2	+1.4	214.4	39.1
2007 SEP 10 14:23	1833	-7.2	179.1	+1.4	214.4	36.3
2007 SEP 10 14:24	1893	-7.5	181.9	+1.4	214.4	33.7
2007 SEP 10 14:25	1959	-7.9	184.7	+1.4	214.5	31.3
2007 SEP 10 14:30	2365	-9.1	196.3	+1.4	214.5	21.4
2007 SEP 10 14:40	3424	-10.1	211.5	+1.4	214.5	13.0
2007 SEP 10 14:50	4646	-10.4	220.3	+1.4	214.5	14.2
2007 SEP 10 15:00	5943	-10.5	225.8	+1.4	214.6	17.1
2007 SEP 10 15:10	7277	-10.4	229.5	+1.4	214.6	19.7
2007 SEP 10 15:20	8633	-10.4	232.1	+1.4	214.6	21.7
2007 SEP 10 15:30	10003	-10.3	234.1	+1.4	214.7	23.2
2007 SEP 10 16:00	14154	-10.2	237.8	+1.4	214.8	26.3
2007 SEP 10 17:00	22534	-10.1	241.4	+1.4	214.9	29.2
2007 SEP 10 18:00	30948	-10.0	243.2	+1.4	215.1	30.6
2007 SEP 10 19:00	39374	-9.9	244.3	+1.4	215.3	31.4
2007 SEP 10 20:00	47805	-9.9	245.1	+1.4	215.5	31.9
2007 SEP 10 21:00	56239	-9.9	245.7	+1.4	215.7	32.3
2007 SEP 10 22:00	64674	-9.9	246.2	+1.4	215.9	32.6
2007 SEP 10 23:00	73109	-9.9	246.6	+1.4	216.1	32.8
2007 SEP 11 00:00	81545	-9.8	247.0	+1.4	216.3	33.0
2007 SEP 11 01:00	89981	-9.8	247.3	+1.4	216.4	33.1
2007 SEP 11 02:00	98417	-9.8	247.6	+1.4	216.6	33.3