PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = " 20041020, C.A. Nixon Initial Version; 20050228, C.A. Nixon Major revision post-peer review; 20060223, SLA/EN, minor cleanup, REF_KEY_IDs changed." OBJECT = DATA_SET DATA_SET_ID = "CO-S-CIRS-2/3/4-TSDR-V1.0" OBJECT = DATA_SET_INFORMATION DATA_SET_NAME = " CASSINI SATURN CIRS TIME-SEQUENTIAL DATA RECORDS V1.0" DATA_SET_COLLECTION_MEMBER_FLG = "N" START_TIME = 2005-09-01 STOP_TIME = "N/A" DATA_SET_RELEASE_DATE = 2006-07-01 PRODUCER_FULL_NAME = "DR. CONOR A. NIXON" DETAILED_CATALOG_FLAG = "N" ARCHIVE_STATUS = "IN PEER REVIEW" DATA_OBJECT_TYPE = "TABLE" DATA_SET_TERSE_DESC = "This data set contains data from the Cassini Composite Infrared Spectrometer Instrument" ABSTRACT_DESC = "This data set comprises uncalibrated and calibrated data from the Cassini Composite Infrared Spectrometer (CIRS) instrument. The basic data is comprised of uncalibrated raw spectra, along with along with pointing and geometry information, and housekeeping information. Also included are calibrated power spectra, and documentation." ABSTRACT_TEXT = "UNK" CITATION_DESC = "Nixon, Conor, Cassini Jupiter Encounter Composite Infrared Spectrometer Data, NASA Planetary Data System, CO-J-CIRS-2/3/4-TSDR-V1.0, 2004." DATA_SET_DESC = " Data Set Overview ================= The Composite Infrared Spectrometer is a dual-interferometer carried on the Cassini spacecraft Remote Sensing Palette. Cassini was launched on 15th October 1997 and due to arrive at Saturn on July 1st 2004. En route to Saturn, Cassini made a gravity-assist maneuver at Jupiter in December 2000, which allowed for a six-month Jupiter observing campaign. CIRS was operated in full science mode for much of this six month period, either as the 'prime' instrument controlling pointing, or as a 'ride-along' when another team was 'prime'. The CIRS Jovian dataset forms the first part of the CIRS archive. The Cassini Prime Mission after SOI (Saturn Orbit Insertion) is the first four years of tour, from July 2004 to July 2008. After that time, if approved and technically possible, an extended mission period will begin. During the first four years of Prime Mission, Cassini will undergo 76 orbits (revs) of Saturn, known as 0, A, B, C, 3 ... 74. The original orbits 1 and 2 were replaced with A, B and C when the mission was redesigned in order to accomodate radio link issues with the Huygens probe, discovered after launch. The probe delivery to Titan is scheduled for rev C. There are 44 targeted (i.e. close) fly-bys of Titan planned during the first 76 revs. See MISSION.CAT file for more information on the Cassini mission. Science Objectives and Observation Strategy ------------------------------------------- The Cassini/Huygens mission to the Saturnian system is designed to investigate the following targets: 1. Saturn 2. Rings 3. Titan 4. Other ('icy') satellites. The overall mission may also be broken in physical target types: 1. Atmospheres (Saturn and Titan) 2. Surfaces (Titan, and other satellites). 3. Magnetosphere: fields, particles and solar wind interaction (Sun-Saturn) 4. Orbital mechanics (rings, satellites esp Hyperion). CIRS contributes to the investigation of many of these areas: SATURN Sensing of tropospheric and stratospheric temperatures and composition. This includes abundances of the major and minor species, the hunt for new gaseous species, isotope ratios for major species, and dynamics. Allocating time for Saturn observations was the responsibility of the Saturn TWT (Target Working Team), which was in charge of much of the periapse parts of each orbit (rev). There was also input from the Atmospheres Working Group (AWG) which dealt with high-level science reccomendations. CIRS Saturn atmospheric science goals are met with observations at a variety of inclinations, range from Saturn and, in some cases, in conjunction with other teams' observations. The standard CIRS requests include: Name Range Details COMPSIT >60Rs Composition sit and stare at 0.5 cm-1 spectral resolution using FP1. Uses all 3 focal planes. Search for oxygen compounds (CO2 and H2O) and new molecules. MIRMAP 25-40Rs Mid-IR maps, centered at a latitude, with the long axis of our arrays (Z) pointed toward the pole of Saturn to allow the planet's rotation to map out a latitude band. 3 cm-1 resolution. FIRMAP 15-25Rs Far-IR maps, constructed by slewing equatorward over a hemisphere. Slews overlap and repeat to map out the entire hemisphere. 15 cm-1 spectral resolution. FTRACK <10Rs Campaign with VIMS and ISS to track features across the disk from limb to limb, including limb sounding. FP1 nadir sounding at 3 cm-1, FP3/4 limb sounding at 15 cm-1. The goal is to study vertical structure and poleward heat transport. LIMBMAP <6Rs Vertical sounding at multiple latitudes on the limb at 15 cm-1. LIMBINT <6Rs Long integrations for vertical composition at one location on the limb. Resolution = 0.5 cm-1 or 1 cm-1 (TBD). NADIROCC<10Rs Helium abundance measurements taken by following the Radio Science Team's occultation points across the disk, 3 cm-1 res. OCCLIMB <6Rs Independent verification of vertical temperature profile at Radio Science's occultation latitudes. REGMAP\ <10 Rs Regional mapping and/or composition feature tracks, to fill COMPFT/ in coverage not obtained by the other observations (0.5 or 3 cm-1) TEMPSIT Early temperature map. Res=3 cm-1. Sit on CML, FP3/4 N-S, let planet rotate to cover all longitudes. Arrays cover Southern Hemisphere (north blocked by rings). MIRCMPSIT Early composition sit and stare. Res = 0.5 cm-1. Sit on CML, FP3/4 N-S, Arrays cover Southern Hemisphere (north blocked by rings). FIRCMPSIT Early far-IR composition. Res = 0.5 cm-1. FP1 centered on South Pole and on mid-Southern latitudes. RINGS Measurement of the infrared spectrum at varying phases, leading to conclusions about ring particle size, shape, composition, distribution and dynamics. Allocation of time for rings observing was carried out by the Rings TWT, in conjunction with the Rings Working Group (RWG). Ring observations are made as a function of ring opening angle, or spacecraft elevation: * Faint Ring Long Integrations. The low optical depths of the faint D, E, F and G rings will pose particular observing challenges for CIRS. These rings are best viewed edge-on because this geometry enhances the instrument fill factor. Low spectral resolution of 15 cm-1 with FP1 provides the best signal-to-noise and should be sufficient for detecting the variations of emissivity with wavelength, which is our primary measurement goal. From close range (~ 10 RS) and small opening angle, the FP1 filling factor will approach 1% when pointed at the F rings ansa. Integrations of ~ 10 minutes should yield usable signals. However, because the F ring is so clumpy, it needs to be sampled at many longitudes before a truly representative spectrum can be obtained. Observations will consist of alternating between both ring ansas every ~30 minutes to achieve the most complete rotational coverage of this ring. The E ring will be observed by pointing FP1 near the orbit of Enceladus, where the long edge-on line of sight through the ring maximizes the fill factor. However, this fill factor will still remain quite low, ~ 10-4, so , detecting the E ring will require many, perhaps 100 or more, hours of integration. On the other hand, because the ring is so thick vertically, the observing range can be quite large (3040 RS). More observing time is available then during these apoapse periods of the tour. The VIMS and UVIS instruments will also require substantial integration on this ring, so E ring observations will be cooperative activities between all of Cassinis optical remote sensing instruments. Unfortunately, the best possible fill factors for the remaining rings, D and G, are still lower than for Ring E. It is unlikely that either will be detected with CIRS. * Composition Integrations. CIRS will determine with unique accuracy the ring spectrum between 50 and 1000 micron. As intimately mixed contaminants significantly influence this part of the spectrum, mixtures derived from the visible and near-infrared spectra will be tested against this new spectrum. Spectra of the three main rings over the full CIRS wavelength range will be obtained to determine possible radial variations in the bulk composition. Two types of observations will be made: high spectral resolution (0.5 cm-1) FP3 emission measurements of the A, B and C rings, and high spectral resolution transmission measurements of the rings with the rings against Saturn. The former can be obtained from large ranges 2040 Rs because of FP3s fine spatial resolution; long integrations of 1020 hours will be obtained on representative locations in each ring. The transmission measurements will be made from 20 Rs at relatively low ring opening angles. This will allow a search for absorption features in the A and C rings, and the Cassini division. The same region of Saturn will be observed in at a similar spatial resolution when the rings are not present, to establish the background. The transmission spectra will be obtained over a series of emission angles. * Stellar Occultations. A handful of stellar occultations are observed by CIRS to directly obtain the ring opacity in the infrared. Only a limited number targets are observable by CIRS, including CW Leo and Eta Carinae. Eta Carinae occultations are only observable during the final month of the tour. Occultations are observed in one FP3 pixel (CW Leo) or one FP4 pixel (Eta Carinae) at 15 cm-1 spectral resolution. * Radial scans. These scans are typically executed between 5 and 20 Rs over a range of spacecraft inclinations, from low (5 deg) to highest possible inclination (75 deg), radial mapping (FP1, FP3) of the rings, on both lit and unlit sides, over a range of spacecraft elevations, inclinations, local times and phase angles, is performed to obtain broadband radiometric measurements of the total flux in the CIRS wavelength range. Sets of observations are obtained in each of the inclined orbit intervals to map the temperature variation in the rings with changing solar illumination. Two types of scans are planned. So called temperature scans will consist of spectra at 15 cm-1 spectral resolution of the lit and unlit sides of the rings at many incidence and emission angles and provide prime information on the ring thermal gradient as a function of radial distance to Saturn. Submillimeter scans will be made of spectra at 1 cm-1 spectral resolution of the lit and unlit sides of the rings to map the thermal characteristics and composition of the ring particles out to 1 mm. * Azimuthal scans. These observations are executed between 5 and 20 Rs at spacecraft inclinations greater than 20 deg. They will be used to study both the surface properties, the vertical dynamics and the spin of ring particles. Observations of the cooling and heating of the ring particles entering and emerging from the planetary shadow are planned to derive particle thermal inertias for all three main rings. It will make measurements at moderate radial resolution (typically 1000 km) across the shadow boundaries at low spectral resolution (15 cm-1) with the FP1 field of view. To constrain the vertical dynamics of ring particles, the temperatures of the main rings will be measured by CIRS along the ring azimuth of the main rings, from the exit of the shadow (morning) to the evening ansa, both on the unlit and unlit faces. This unique experiment will be realized with spectra at low spectral resolution (15 cm-1). Spins create both an azimuthal asymmetry in the ring temperature and a dependence of the temperature with the emission angle, due to day/night contrast. Circumferential scans at a variety of phase and emission angles will be executed to detect azimuthal asymmetries and the anisotropy in the ring particle emission function which are both function of particles spin and thermal inertia. Occasionally, when observing time is highly disputed, long azimuthal scans (8-to-20 hours long depending on geometry and face) will be replaced by a series of radial scans at different azimuths. TITAN Sensing of tropospheric and stratospheric temperatures and composition. This includes abundances of the major and minor species, the hunt for new gaseous species, isotope ratios for major species, and dynamcics. CIRS may also be able to sense the surface near 600 cm-1. Allocation of time for Titan observations was primarily done in the TOST group (Titan Orbiter Science Team), in conjunction with recommendations from the AWG. CIRS can achieve different science goals at different distances from Titan. Typically, CIRS makes the following requests (symmetric about closest approach): + 0 to +10 mins HIRES surface mapping (e.g. slew over south pole). +10 to +45 mins FIRLMBT - radial limb scans with FP1 to derive temperatures in the 8--100 mbar region via the N2-N2 collision-induced absorption between 20--100 cm-1. +45 to +75 mins FIRLMBAER - radial limb scans with FP1 to measure/ characterize particulate and condensate distributions, abundances and properties. +75 to +135 mins FIRLMBINT - integrate at two altitudes on the limb with FP1 to search for signals of CO, H2O and new species. +2:25 hrs to +5 hrs FIRNADMAP - slow scan north-south or east-west on the disk to sound tropospheric temperatures at 40--200 mbar, via the N2-N2 absorption, OR, slow scans at constant emission angle on the disk, to retrieve surface temperatures in the presence of aerosols around 520 cm-1. +5 to +9 hrs MIRLMBMAP - map 1/4 limb using the FP3 and FP4 arrays, to infer stratospheric temeratures via the 1304 cm-1 band of CH4. The arrays are placed perpendicular to the limb at two altitudes, chosen to provide overlapping coverage of the altitude range 150 to 420 km. The arrays are used in blink (ODD-EVEN) mode. After mapping both altitudes, the arrays are stepped 5 degrees in latitudes for the next step. OR, MIRLMBINT - as in MIRLMBMAP, except that only a single latitude is covered, at two over-lapping altitudes for 2 hrs in each position. To search for and measure new species in the mid-IR: methyl, benzene etc +9 to +13 hrs FIRNADCMP - integrate on the disk at emission angle approximately 60 degrees with the FP1 detector, in order to measure spatial abundance distribution of weak species and search for new species in the far-IR. +13 to +22 hrs MIDIRTMAP - scan the entire visible disk with the FP3/FP4 arrays perpendicular to the scan direction ('push-broom'), to measure stratospheric temperatures via the CH4 v4 band. Used for later dynamical analysis, for winds, waves etc. +22 to +48 hrs COMPMAP or TEMPMAP - map a meridian across the planet either E-W or N-S, using the Fp3/FP4 arrays in two positions longwise. To search for new species, and/or monitor temperatures. ICY SATELLITES Surface mapping in the IR, providing information on the surface composition, morphology, and age. Close passes of icy satellites resulted in time allocated to the SOST (Satellites Orbiter Science Team), which divided the time between teams. There was also input from the Surfaces Working Group (SWG). During the Cassini tour, there are eight flybys of the classical icy satellites targeted at 1000 km or less, as well as a number of 'Voyager-class' (less than 300,000 km) encounters. There are also flybys of several much smaller satellites, such as Janus and Epimetheus, at various distances. The dimensions of these objects range from less than 100 km to as much as 1530 km (for Rhea). Consequently, it is most useful to discuss CIRS observations in terms of the angular diameter of the object, rather than its distance from the spacecraft. Normally the spacecraft orientation is controlled by momentum wheels, which provide pointing accuracy and precision of ~2 mrad and ~0.04 mrad, respectively. Consequently, the full spatial resolution of the FP3 and FP4 pixels (0.3 mrad) cannot be utilized with reasonable confidence until the target exceeds 1 mrad in diameter. At that point, the separation of focal planes 3 and 4 (0.9 mrad), and the large size of FP1 (nominally 3.9 mrad) offer reasonable assurance of obtaining useful data in either FP1 or at least one of FP3 and FP4. As with the planet and the rings, the order of magnitude difference in FOV scale between FP1 and the other focal planes plays heavily in the design of the icy satellite observations. Approaching from a distance, CIRS observations might proceed roughly in the following order. FP1INT, FP34INT: Compositional integrations (typically performed at ranges where the target AD is 1-3 mrad). Because spectral features of solid materials are generally broader than those of molecular lines, these observations are made at 1-3 cm-1 resolution. Conducted in staring mode, using FP1 and center detectors of FP3 and FP4, these are concentrated in geometries with low phase angles, so as to view the icy satellite surfaces at their warmest and maximize the signal-to-noise ratio. The steep rolloff of intensity with increasing wavenumber requires increasing integration time to extend the spectrum. For a 100K surface and a spectral resolution of 3 cm-1, a SNR of 10 at 600 cm-1 can be obtained with 1 minute of integration, but extending the spectrum to 800 cm-1 with the same SNR requires integration of 100 minutes Therefore, extending the spectrum to the highest wavenumbers will involve coadding spectra over the entire tour. SECLN, SECLX: Satellite eclipse entry (N) or exit (X) observations (AD>1 mrad, phase angle phi <100 degrees, spectral resolution delv = 15.5 cm-1; a typical eclipse duration is ~2 hours). The high sensitivity of FP1 permits observations of objects even when the FOV is incompletely filled, or when the phase angle is moderately high. At low phase angles, even FP3 can be used to follow the initial portion of the cooling curve for relatively dark objects; this allows observations with body-centric spatial resolution better than 10o to be made when the apparent target size exceeds ~3 mrad. Eclipses provide the thermal inertia of the upper mm or so of the surface, as well as estimates of surface coverage by relatively large fragments of consolidated material. FP1FAZ: Phase/longitude (diurnal cycle) coverage (AD>1 mrad, delv=15.5 cm-1, 10-20 minutes). Focal plane 1 will be utilized to determine the disk-averaged temperature of the satellites. From the resulting diurnal behavior, mean thermal inertias in the upper cm or so of the surface will be derived. FP34FAZ, FP34MAP, FP34REG: Global thermal inertia mapping and/or hot spot monitoring (AD>3 mrad, delv=15.5 cm-1). Maps are made by slewing and rastering FP3 and FP4 across the disk at rates not to exceed that for Nyquist sampling (16 microrad/sec in blink mode); observation durations will typically be 10-30 minutes. These maps will be successful for varying portions of a satellite, depending on its albedo and thermal inertia. The exception is Enceladus, which is so cold that even the subsolar regions will be barely detectable in an individual measurement. In this case, mapping will serve to monitor the satellite for ongoing endogenic activity; for example, active sources at or above the NH3.H2O eutectic temperature will be easily observed if they fill more than a few percent of an FP3 or FP4 pixel. FPGREEN: Search for a solid state greenhouse (AD>10 mrad, phi <40 degrees, delv =15.5 cm-1, 15 minutes). The decreasing absorption coefficient of water ice with decreasing wavenumber in the far-IR permits detection of radiation from increasingly far below the surface, reaching as deep as 1 cm at 10 cm-1. Slow east-west slews using FP1 allow following the daily penetration of the thermal wave into the regolith. FP1POLE: Polar night (annual cycle) coverage (AD>10 mrad, delv=15.5 cm-1, 15 minutes). FP1 observations of the dark winter polar region from high latitude permit determination of the seasonal cooling curve. This enables an estimate of thermal inertia in the upper tens of cm of the polar regolith. FP1DAYMAP, FP1DRKMAP: Hemispheric FP1 mapping near closest approach (AD>10 mrad, delv=15.5 cm-1). The high sensitivity of FP1 permits rapid mapping of satellite disks near closest approach, where time is at a premium. Nyquist-sampled maps at low spectral resolution (slew rate 400 microrad/sec) will typically take 10-30 minutes. These permit identification of minor thermal anomalies, even on the night hemisphere. Other TWT and WGs The cross-discipline TWT (XD TWT) allocated time near apoapse on some revs. The magnetospheres TWT allocated critical time for magnetospheric observations, such as time near critical transition boundaries. Instrument Overview ------------------- CIRS consists of two interferometers; a far-IR polarizing interferometer sensitive from 10-600 cm-1, and a mid-IR interferometer sensitive from 600 -1400 cm-1. The far-IR radiation is sensed by a large (~4 mrad diameter) thermopile detector (actually two, one for reflected and one for transmitted beam at the polarizer/analyzer), known as FP1. The mid-IR radiation falls on two 1X10 arrays, known as focal planes 3 & 4. FP3 is an array of photoconductive detectors sensitive from 600-1100 cm-1, and FP4 is an array of photovoltaic detectors seneitive from 1100-1400 cm-1. FP2 was dropped from the original design. Each of the 1X10 arrays has a 5-channel amplifier/signal processor, meaning that only 5 of the 10 detectors in each array can be used at a time. The maximum number of simultaneous interferograms from CIRS is therefore 11 (1 from FP1, 5 from FP4, 5 from FP4). However, there are observing modes in which some of the focal planes are not used, leading to a lesser number of active channels. Almost the entire instrument is thermostated to 170 K, including the primary and secondary mirrors, internal optics, scan mechanisms, and the FP1 focal plane assembly. The only exception is the FP3 and FP4 arrays (the mid -IR FPA), which are cooled by a passive radiator to between 74 and 85K. See the INST.CAT file for full details. Calibration Overview -------------------- Wavelength calibration is achieved by use of a reference diode laser interferometer which uses the same scan mechanism as the IR interferometer. Careful attention must be paid to the laser mode and voltage which may drift/mode jump. Radiometric calibration in the far-IR (FP1) is simplified due to the fact that there is only one temperature inside the instrument. Therefore, use of a deep space (2.7 K) reference target is sufficient to calibrate radiance. The fact that the mid-IR has two temperatures to contend with means that a second reference target is required. Therefor, in the mid-IR optical path, a shutter may be lowered for calibration purposes, which gives a 170K reference body. Calibration must be done using complex number algebra and fourier transforms, to correctly account for phase changes which occur in the beamsplitter. See the DATASIS.TXT for details. Parameters ---------- The major parameters when observing with CIRS are as follows: 1) mid-IR shutter (open or closed). This is used for radiometric calibration in the mid-IR, which requires two thermal reference bodies (space and shutter). 2) mid-IR focal plane temperature set point (74-85 K). This was usually set to the lowest level in the range at which the radiator could cope with heating from the sun and/or Saturn/rings, and therefore, achieve stability of FPA temperature. 3) FP3 pixel mode (ODD, EVEN, CENTER, PAIRS). Odd mode: detectors 1,3,5,7,9 active. Even mode: detectors 2,4,6,8,10 active. Center mode: detectors 3,4,5,6,7 active. Pairs mode: 1&2, 3&4, 5&6, 7&8, 9&10 signals combined and amplified. 4) FP4 pixel mode (ODD, EVEN, CENTER, PAIRS). As FP3 modes, except that detectors 4,5,6,7,8 used in CENTER mode, to spatially match the detectors of FP3 which are numbered in reverse physical order. 5) co-add mode (COADD or NO-COADD). In co-add mode, two successive scans are added together in the on-board electronics (buffers), to reduce the data rate by half. Data ---- This dataset is composed of CIRS Time Sequential Data Records, and related calibration software. READOUT, DOWNLINK AND DECOMPRESSION CIRS data is normally read out at a rate of 4 kilobits per second (kbs) and 8kbit packets are transfered via the Bus Interface Unit (BIU) to the spacecraft Command Data Subsystem (CDS) every 2 seconds. CIRS has many ways of reducing data rate, such as co-adding IFMs (reduces rate by factor 2), dropping FP3 or FP4 readout (reduces by 45%), dropping FP3 and FP4 readout (reduces by 91%), or going to housekeeping only mode. Data packets are compressed in the instrument electronics, packetised on the spacecraft, transmitted to the Earth via the Deep Space Network (DSN) and then decompressed by software on the ground. At this stage, the data goes into a processing pipeline, which organizes the science data into binary tables and interpolates housekeeping records. Pointing and genometry tables are also produced when the NAIF data becomes available. VANILLA PROGRAM FOR READING TABLES The data is in the form of binary tables, also known as the Vanilla database. Vanilla is a simple database access tool, also included on each volume as both source and executable. Note however that the Vanilla software is NOT REQUIRED in order to read the binary data, but it may simplify the task. Notably, Vanilla links together all binary files into a huge, `logical' table, which can be searched based on key fields. However, the user may read the binary data directly, using any programming language desired. If this approach is taken it is extremely important to pay attention to binary field widths: field widths vary, and typically trying to read an entire record into a data structure will fail: due to assumed padding of fields. The user must read the data in field by field, specifying width. Field widths are described in the *.FMT files, which are placed in each data directory. Some tables have both fixed-length and a variable-length fields. In this case, the variable length part of the record is stored separately, in a file with the same name but an extension .VAR, instead of .DAT. The third type is file extension is .LBL, which is the PDS detached label. DATA LEVELS The level-0 tables (base level) are contained in /DATA/UNCALIBR. These are described in detail in the document DATASIS.PDF (DATASIS.TXT). These tables types (IFGM, OBS, IHSK, FRV) are essentially the raw-level information which came from the instrument: the only process applied was unpacking (uncompressing) the instrument packets and, in the case of the housekeeping data, interpolating the 64-sec interval housekeeping data onto the science scan intervals. Original housekeeping data is stored in /DATA/HSK_DATA, which is read out at 64-sec intervals when the instrument is either ON or in SLEEP mode. Pointing and geometry information is stored in /DATA/NAV_DATA. These tables are described in detail in the DATASIS document, and also in the FMT format files in the NAV_DATA area. Primarily, these store the spacecraft attitude and position w.r.t. major bodies (GEO file type), the position of the 11 detectors (99 q-points, or fiducial reference marks) on all bodies in the FOV (POI file type), and the list of bodies seen in each detector (TAR type). Pointing and geometry information is derived from the spacecraft re-constructed attitude ('C') and trajectory ('SPK') kernels, using NAIF (Navigation and Ancillary Information Facility) toolkit routines supplied by JPL. Calibrated spectra are stored in two variations: apodised and unapodised. These are stored in /DATA/APODSPEC and /DATA/UNAPSPEC respectively. Apodisation is the process of mathematical filtering or smoothing, which removes `ringing' effects from finite-width mathematical FFTs, widening the instrument line shape in the process. Either form is valid for science, depending on personal preference. Apodization will normally use the Hamming function window, but other types may be used and the type will be given in the tables. " CONFIDENCE_LEVEL_NOTE = " This volume represents a first attempt at calibrating the CIRS Jupiter dataset. Certain calibration problems are known to exist, in particular, thermal drifts in the ATMOS02B map noticable at the 1-2 K level, which are seen as 'striping'. Similar drifts are likely to be present in other areas. Hence, the absolute radiometric accuracy is unlikely to be better than 1%. If a way is found to adequately remove these effects, it is envisaged that a second edition of the data would be produced. The spectral calibration is thought to be accurate to approximately 0.1 cm-1. NOTE ON INTERFERENCES CIRS interferogram data suffers from a number of external interferences, especially: - a 8 Hz spike pattern due to the spacecraft clock ticks. - a 1/2 Hz spike pattern due to the Bus Interface Unit, transfer of data. - a sine wave of variable frequency which appears correlated with the electronics board temperature. - scan speed fluctuations which have been traced to two mechanical vibrations on the spacecraft: (a) the MIMI LEMMS actuator (b) the reaction wheels used to turn the spacecraft. These various effects are described in more detail in the cirs_interferences.pdf document found in the DOC directory. 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