J/ApJS/244/14 Cassini CIRS observations of Titan 2004-2017 (Nixon+, 2019)
Cassini Composite Infrared Spectrometer (CIRS) observations of Titan 2004-2017.
Nixon C.A., Ansty T.M., Lombardo N.A., Bjoraker G.L., Achterberg R.K.,
Annex A.M., Rice M., Romani P.N., Jennings D.E., Samuelson R.E.,
Anderson C.M., Coustenis A., Bezard B., Vinatier S., Lellouch E.,
Courtin R., Teanby N.A., Cottini V., Flasar F.M.
<Astrophys. J. Suppl. Ser., 244, 14 (2019)>
=2019ApJS..244...14N 2019ApJS..244...14N
ADC_Keywords: Planets; Spectra, infrared
Mission_Name: Cassini
Keywords: infrared: planetary systems ; instrumentation: interferometers ;
planets and satellites: atmospheres ;
planets and satellites: individual (Titan) ;
space vehicles: instruments ; techniques: spectroscopic
Abstract:
From 2004 to 2017, the Cassini spacecraft orbited Saturn, completing
127 close flybys of its largest moon, Titan. Cassini's Composite
Infrared Spectrometer (CIRS), one of 12 instruments carried on board,
profiled Titan in the thermal infrared (7-1000µm) throughout the
entire 13yr mission. CIRS observed on both targeted encounters
(flybys) and more distant opportunities, collecting 8.4 million
spectra from 837 individual Titan observations over 3633hr.
Observations of multiple types were made throughout the mission,
building up a vast mosaic picture of Titan's atmospheric state across
spatial and temporal domains. This paper provides a guide to these
observations, describing each type and chronicling its occurrences and
global-seasonal coverage. The purpose is to provide a resource for
future users of the CIRS data set, as well as those seeking to put
existing CIRS publications into the overall context of the mission,
and to facilitate future intercomparison of CIRS results with those of
other Cassini instruments and ground-based observations.
Description:
We define two common terms used to distinguish major types of
Cassini's Composite Infrared Spectrometer (CIRS) observations: nadir
and limb. A nadir observation was one where the detector field of view
intersects Titan's surface (not necessarily normal to the surface),
whereas a limb observations pointed the detector(s) just outside the
disk of Titan's solid body and measured the atmosphere only, between
the surface and the exobase at around 1500km. To obtain a nadir map in
the far- or mid- infrared, the detector(s) was (were) swept up and
down in parallel tracks in the Z direction, with offsets in X. A limb
profile (vertical cross-section) could be obtained with FP1 by moving
the detector in a radial direction, from the surface outward. See
Section 3 for further explanations.
The following information is correct at the time of writing; however,
the Planetary Data System (PDS) is an evolving internet archive and
hence tools and data accessibility may have changed since publication.
Cassini CIRS data is distributed via two sites: the Atmospheres Node
and the Rings Node.
http://pds-atmospheres.nmsu.edu/data_and_services/atmospheres_data/
Cassini/inst-cirs.html
http://pds-rings.seti.org/cassini/cirs/
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table4.dat 75 141 Titan Flyby data
table5.dat 78 147 CIRS far-infrared limb observations; updated
from erratum published in 2021, ApJS, 257, 70
table6.dat 88 104 CIRS mid-infrared limb observations; updated
from erratum published in 2021, ApJS, 257, 70
table7.dat 92 143 CIRS far-infrared nadir maps and UVIS EUVFUV; updated
from erratum published in 2021, ApJS, 257, 70
table8.dat 80 173 CIRS far-infrared nadir integrations; updated
from erratum published in 2021, ApJS, 257, 70
table9.dat 78 174 CIRS mid-infrared nadir maps; updated
from erratum published in 2021, ApJS, 257, 70
table10.dat 64 102 CIRS distant Titan observations; updated
from erratum published in 2021, ApJS, 257, 70
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See also:
J/ApJ/724/L84 : Changes in Titan's atmosphere from Cassini (Teanby+, 2010)
J/ApJ/792/118 : Protonated oxirane characterization
J/ApJS/191/96 : IR spectra and optical constants of nitrile ices (Moore+, 2010)
J/A+A/557/L6 : Spectra of the Titan haze at 1-5 micron (Kim+, 2013)
J/A+A/573/A21 : Extinction of Titan haze at 3 micron (Courtin+, 2015)
http://pds-rings.seti.org/cassini/cirs/ : Cassini CIRS Ring-Moon Systems Node
http://pds-atmospheres.nmsu.edu/data_and_services/atmospheres_data/Cassini/
inst-cirs.html : CIRS data on the NASA PDS Planetary Atmospheres Node
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Rel [1/16] Release subset (1)
4- 7 A4 --- Flyby Flyby number
9- 11 A3 --- Orbit Orbit number or Rev
13- 22 A10 "M/D/Y" Date Observation Date
24- 26 I3 d DOY [1/366] Observation Day of Year
28- 35 A8 "h:m:s" Time Time at closest approach
37- 42 I6 km Alt [878/694947] Altitude
44- 47 A4 --- Illum Inbound or Outbound Illumination
49- 51 A3 --- Saturn Approximate direction wrt Saturn ("In" or "Out")
53- 57 F5.2 h Sol [0/24] Local Sol time, Dec-Hr
59- 63 F5.1 deg LAT [-83/87] Closest approach latitude
65- 69 F5.1 deg LON [0.5/360] Closest approach longitude
71- 75 F5.1 deg Phase [11.9/171.4] Phase at closest approach
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Note (1): Release subset as follows:
1 = Saturn Orbit Insertion/Probe Release;
2 = Occultations;
3 = Petal Rotations / Magnetotail Passage;
4 = Pi-Transfer;
5 = Icy Satellites;
6 = High Inclination, outbound;
7 = High Inclination, inbound;
8 = Saturn Equinox Viewing;
9 = Icy Satellite Flybys and Ansa-to-Ansa Occultations;
10 = High Northern Titan Ground tracks;
11 = Inclined - 1;
12 = Equatorial - 1;
13 = Inclined - 2;
14 = Equatorial - 2;
15 = Inclined - 3;
16 = F Ring/Proximal Orbits.
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Byte-by-byte Description of file: table[56789].dat table10.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- Flyby Flyby number
6- 34 A29 --- Obs Observation name
36- 45 A10 "M/D/Y" Date Observation Date
47- 49 I03 d DOY [1/363] Observation Day of Year
51- 58 A8 "h:m:s" Time Start Time
60- 64 A5 "h:m" Dur Duration
67- 90 A24 --- LAT Pointing (Center Latitude Longitude) or comment
92 A1 --- f_LAT [*] Note on LAT (1)
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Note (1): Flag as follows:
* = Where the observation track is offset from the subspacecraft point,
the midpoint of the scan is given.
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History:
From electronic version of the journal
21-Aug-2020: Insert into VizieR
28-Dec-2021: Tables 5-10 updated from erratum
published in 2021, ApJS, 257, 70
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 13-Feb-2020