← back to ‘Outer Moons of Saturn’ (Methods)
Cassini ISS data of Saturn’s irregular moons XXX xxxx. The solar-analog stars 16 Cygni B and HD 71334 as well as Titan’s cloud deck were imaged for the purpose of calibration of Cassini Imaging data of the irregular moons. Xxxxx xxxx xxxxx.
Table of contents(1) Xxxx |
 |
 |
Fig. (middle): Composite of three Cassini images of star 16 Cygni B (inside circles). The similarly bright object directly above 16CygB is its companion 16 Cygni A.
Fig. (right): Xxxx xxxx xxxx.
This page describes the calibration of the Cassini Imaging (ISS) data of the irregular moons of Saturn. Needless to say that it is still under development. This note will be removed as soon as most of the intended content is added.
Last update: 01 Jan 2019 — page content is best displayed on a screen at least 1024 pixels wide
(1) Xxxxxx
Calibration xxxxx.
(2) Cassini observations: Overview
Table of contents:
(A) Availability of Cassini observations
(B) Imaging observations (ISS)
Note: ISS is the abbreviation for the Cassini cameras (Imaging Science Subsystem) and has nothing to do with the International Space Station which was named ISS many years later. A high-level instrument’s description is given in Porco et al. (2004).
(A) Availability of Cassini observations
General overview on product and data availability. Xxxx xxxx xxxx xxxxxx. For imaging (ISS) high-level planning details → section (8).
| Cassini observations | yes | (xxxx) |
| Xxxxx | yes | (xxxxx) |
| xxxxx | no | — |
(B) Imaging observations (ISS)
General data-acquisition overview for calibration:
| No. of observation requests used for cal. | — | 7 (2 primes; 3 riders; 2 coincidently useful obs.) |
| Observation dates | — | 03/2012 – 11/2016 |
| Apparent visual magnitudes | — | 6.2 mag (16CygB); 7.8 mag (HD71334) |
| Distances to Cassini | — | ∼2000 km (Titan) – 124 lightyears (HD71334) |
| Xxxxx | — | xxxxx |
| Approx. number of images | — | 363 star images; 20 Titan flats; 20 0-ms exposures |
Detailed ISS planning → sheet (8)
(8) Cassini ISS observations: Planning
Table of contents:
(A) Table: Calibration observations overview
(B) Map: 16CygB and HD71334 in the sky of Cassini
(C) Titan geometry
General overview on ISS planning
→ sheet (2B)
High-level camera planning commands:
(includes five IOI files with post-downlink notes plus ISSPT screenshot for one request) [ not yet available ]
Fail notes (Cassini ISS)
– none (just one data gap over the calibration star in one image)
(A) Table: Calibration observations overview
Observational circumstances and geometry information for the five ISS observations intended for data calibration of the irregular moons of Saturn.
Notes XXXXXXXXXX:
a The naming scheme used for Cassini Solstice Mission observations (“requests”) gives information on the object (first three letters), the request’s primary goal (Rot = rotation period), and the approximate observation phase angle (three digits). The three digits between the first and the second underline indicate Cassini’s orbit number. “OT” stands for “other target”.
b Rev. = revolution = Cassini orbit number; peri = periapsis segment. Note that (for some reasons) the true number of orbits since Saturn arrival in 2004 is off (ahead) by 1.5 compared to the official count which is noted here and used in all technical aspects.
c Time difference between shutter mid-time of first and of last image used for the lightcurve.
d A uniform Earth-to-object distance of 1.319·109 km (range at opposition in April 2013) is used here for the distance between the irregular moons and Earth.
e For full-resolution images. The values must be doubled when the NAC was operated in 2×2 summation mode.
f Calculated from the absolute magnitude H, the observation phase angle α, and the distances of XXXXX to the sun and to Cassini.
g Coordinates of the irregular moons (geocentric RA/Dec and ecliptic λ/β) as seen from Cassini during the observations, see also sheet 8B.
h Phase-angle bisector vector (longitude and latitude). For definition and use, see appendix in Harris et al. (1984).
(B) Map: 16CygB and HD71334 in the sky of Cassini
16CygB and HD71334 as seen from Cassini (and also from Earth). Orthographic projection of the sky; geocentric coordinate system (RA/Dec).
Shown are the locations of the two stars (light-yellow circles with annotations), the location of the sun from 2004 to 2017 (smooth sinusoidal line from RA ∼ 290° to ∼ 85°; the sun moves from right to left), the Milky Way (yellow band) and the Magellanic clouds (yellow spots to the lower right), the ecliptic poles (gray diamonds), and Saturn’s poles (gray diamonds).
NP = north pole; SP = south pole.
(C) Titan geometry
DIGIT plots of Titan viewing geometry while the images for flatfielding were taken.
Notes:
– The field-of-view of the scenary in all four panels is 60°×110°.
– The information at lower left in each panel (“NEG_X”) indicates the orientaton of the spacecraft’s secondary axis.
– The small white square is the field-of-view of the WAC (wide-angle camera); the blue inside of the VIMS spectrometer, and the tiny white dot inside is the field-of-view of the NAC which has taken images.
(9) References for calibration
Wikipedia:
16 Cygni 
16 Cygni
HD 71334
Titan Titan
My ‘Outer Moons of Saturn’ site: Sheet ‘links and references’
West, R.A., Knowles, B., Birath, E., Charnoz, S., Di Nino, D., Hedman, M., Helfenstein, P., McEwen, A., Perry, J., Porco, C.C., Salmon, J., Throop, H., Wilson, D. (2010): In-flight calibration of the Cassini imaging science sub-system cameras. Planet. Space Sci. 58, 1475-1488.
Porco, C.C. West, R.A., Squyres, S.W., McEwen, A.S., Thomas, P.C., Murray, C.D., Del Genio, A., Ingersoll, A.P., Johnson, T.V., Neukum, G., Veverka, J., Dones, L., Brahic, A., Burns, J.A., Haemmerle, V., Knowles, B., Dawson, D., Roatsch, Th., Beurle, K., Owen, W. (2004): Cassini imaging science: Instrument characteristics and capabilities and anticipated scientific investigations at Saturn. Space Sci. Rev. 115, 363-497.
West, R.A. (2002): Cassini ISS Image Calibration: Theoretical Basis. pdf file on Planetary Data System Imaging node.
West, R.A., McEwen, A.S. (1998): Cassini ISS In_Flight Calibration Plan. pdf file on Planetary Data System Imaging node.
© Tilmann Denk (2019)