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CASSINI S MIMI INCA SENSOR CALIBRATED DATA V1.0 (PDS)

NSSDCA ID: PSFP-00685

Availability: Archived at NSSDC, accessible from elsewhere

Description

This description was generated automatically using input from the Planetary Data System.

Data Set Overview

The Ion and Neutral Camera (INCA) obtains remote images of the global distribution of energetic ions for energies from 7 keV/nucleon to 8 MeV/nucleon, discriminated according to energy and mass species (oxygen and hydrogen). To obtain the images, INCA measures the arrival directions, energy and mass species of Energetic Neutral Atoms (ENA's) using the relatively new technique of ENA imaging. INCA also can be commanded to obtain very high sensitivity ion measurements, providing the angular, energy and species distributions of in-situ O and H ions. INCA image data are available in three different flavors, each flavor being simultaneously generated. High spatial resolution images have a larger number of pixels than other INCA images (up to 64 by 64), but are available for fewer numbers of energies (usually just 2 energy channels) and are taken at lower time resolution (one image every 4 sectors). High time resolution images are acquired each sector, but have lower spatial resolution (usually 16 by 16 pixels)High time-of-flight and mass resolution images are taken for 9 energy ranges, but only every 4 sectors and with lower spatial resolution. In neutral mode, which is used to obtain ENA images, alternate collimator plates are charged to a high positive and negative voltage, and these collimators sweep up ions and electrons entering the sensor. Neutral atoms pass by the collimators through a slit. Alternately, in ion mode, the collimators are not charged and the ions and electrons pass into the detector. The Cassini Magnetospheric Imaging Instrument(MIMI) Imaging Neutral Camera (INCA) calibrated data set includes all image data collected from the MIMI Data Processing Unit during the Saturn tour. The original data has been decommutated, decoded, calibrated and further processed by software at the Applied Physics Laboratory (APL). The calibrated image data is provided in three forms: an averaged form where the original image N x N pixel images pixels intensity are averaged to a single value for one species and time-of-flight (TOF) combination, browse images which display rows and columns of images for one species and TOF combination, and movies which display averaged ENA image skymaps. Calibration of INCA data has been described fully in the Cassini/MIMI Data User Guide. [VANDEGRIFFETAL2012] This data set should be among the first used by a user of any of the MIMI INCA archive as it will lead one to information required to search for more detailed or highly specialized features in the original data. Parameters ========== This data set comprises image pixel angle averages where the original image N x N pixel image (where N is usually 16, 32 or 64) images pixels intensity in are averaged to a single value for one species and TOF combination. The value displayed is the image intensity in counts/(centimeters squared*steradian*seconds*keV). These are called angle averages since each image pixel has a particular look direction out of the INCA instrument specified in azimuth and elevation. The azimuth directions range from -45 to 45 degrees over the index range 0 to N, where N is the number of rows in the image. The elevation values for each pixel range from 60 to -60 degrees (note: this is backwards) over the index range 0 to N, where N is the number of columns in the image. The pixel sizes are different depending on the resolution of the image. Also note that the look direction angles for each pixel are relative to the center of the INCA image, which may be offset from its nominal center due to the way images are integrated on the spacecraft. The registration of an INCA image against the sky in a specific coordinate system involves proper interpretation of the offset of the image center from its nominal direction. Full details describing this process has been described fully in the Cassini/MIMI Data User Guide. [VANDEGRIFFETAL2012] The standard product ID's are: MIMI_INCA_ANGAVE_S for the high spatial resolution angle averages MIMI_INCA_ANGAVE_T for the high time resolution angle averages MIMI_INCA_ANGAVE_M for the high mass TOF resolution angle averages The data is organized in time by the spin of the spacecraft. When the spacecraft is in staring mode then the MIMI DPU automatically creates a virtual spin that divides the time collection periods into 16 sectors, 16 subsectors, and 16 microsectors and maintains a simple organizational structure for characterizing the collection of the time into time segments. When the spacecraft is spinning at a minimally defined spin rate (adopted by the MIMI DPU) then the MIMI data is automatically segregated into 16 sectors, 16 subsectors, and 16 microsectors. The INCA instrument collection times are then also keyed to these values. The high spatial and high mass TOF image averages are collected over 4 sectors and the high time resolution image averages are collected over 1 sector. Each file contains all the species and tof combination image angle averages for one image resolution type. The resolution type, species and TOF values are included in the parameter set. In addition, this data set includes two types of browse products. One product type is a PNG file containing three rows by N columns of panels, where the bottom three rows are a continuation in time of the top three rows. Each row contains spin averaged high spatial ENA image skymaps (each one accumulated over four sectors), displayed for one species and TOF combinations. The other browse product type is a PNG file containing 1 up to 10 columns, high TOF browse ion thumbnail images displayed for seven time-of-flight ranges (rows) for one species. The value displayed is the log of the image intensity in counts/(centimeters squared*steradian*seconds*keV). The standard product ID's are: MIMI_INCA_ENAIMG_HO for the ENA image skymaps MIMI_INCA_IONANG_H for the ion hydrogen image thumbnails MIMI_INCA_IONANG_O for the ion oxygen image thumbnails The data set also contains MP4 movies which display averaged ENA image skymaps (averaged over a variable, listed number of original on-board images), for one species and TOF combination. The value displayed is the log of the image intensity in counts/(centimeters squared*steradian*seconds*keV). The standard product ID's for the movies are MIMI_INCA_ENAMV_SH0 for the high spatial resolution hydrogen low TOF movies MIMI_INCA_ENAMV_SH7 for the high spatial resolution hydrogen high TOF movies MIMI_INCA_ENAMV_S00 for the high spatial resolution oxygen low TOF movies MIMI_INCA_ENAMV_S07 for the high spatial resolution oxygen high TOF movies MIMI_INCA_ENAMV_TA0 for the high time resolution low TOF movies MIMI_INCA_ENAMV_TA7 for the high time resolution low TOF movies Processing ========== Data in this data set were processed by the use of a number of software programs which calibrate the images to differential intensity, calculate the image angle averages, and display the images in either the skymap or thumbnail display. The skymap and thumbnail images are further processed by averaging the images together and displaying them in rows and columns in browse products which reduces a days worth of images to a few pages. The display software makes use of the JPL Naif SPICE software which contains algorithms to handle the various spacecraft rotation modes. The MIMI team has created and maintain an analysis SPICE kernel set which is available on the MIMI website. The many useful frames of reference fordisplaying the INCA images with celestial bodies have been included in the frame kernel. The SPICE frames used in the products described here have been explained in the coordinate system section below. The skymaps are created by transforming the original image into the following SPICE reference frame. The skymap frame is a dynamically defined frame, XINCA_BORESIGHT_CENTERED, which is defined in the Coordinate Systems section below. Creation of the skymap and thumbnail image displays starts with the calculation of each original image pixels look direction in aximuth and elevation, based on the INCA boresight vector as well as the azimuth and elevation offsets if applicable based on image collection mode. The pixel matching the look direction in the skymap or thumbnail display frame is calculated and the original image pixel intensity value is loaded into the display frame pixel. The thumbnail images are created by transforming the original images into the INCA azimuth and elevation SPICE reference frame. The definition of the thumbnail frame, CASSINI_MIMI_INCA_LL is described in the Coordinate Systems section below. The elevation of the image goes from -60 degrees at the bottom to 60 degrees at the top of the image. The azimuth of the image goes from -45 degrees on the left to 45 degrees on the right. The MP4 movies are created using the skymap display software to output consecutive ENA skymaps in time. The QuickTime software was used to convert the PNG files into the movies. Typically the movies display the INCA image data in the Saturn frame, XINCA_SATURN_CENTERED which is described in the Coordinate System section below. The Titan frame, XINCA_TITAN_CENTERED, is used to display the images for the Titan flybys. It is also described below in the Coordinate System section. The use of the Saturn centered or Titan centered frame improves the continuity of movies because it reduces the effect of the spacecraft motion on the movie. Data ==== The MIMI INCA calibrated data set includes image angle averages, browse images and movies. The image angle averages are an ASCII CSV table. Each table contains variable length records for which the fields are comma delimited. INCA Image Angle Average Data --------------------------Fields include: a purpose identifier where science data records are identified with purpose = sci starting and ending ephemeris times Spin, sector, subsector (and for INCA Fine Rate (FRT) data microsector) SCLOCK and spin period that are used to derive the starting ephemeris time Notes regarding the SCLOCK value: 1. Only the SCLOCK major segment value is provided - MIMI currently does not have access to the fine SCLOCK value hence SCLOCK resolution is limited to +- 1/2 SCLOCK count 2. The SCLOCK is only available from telemetry at the beginning of each spin. All other published SCLOCKS are derived from the spin starting SCLOCK, the spin numbers (for the current and next available spins), and the spin period. 3. SCLOCK values are assumed to drive the value of the ephemeris times and not vice-versa. All effort is made to validate the published ephemeris times but since updates to the Cassini SCLOCK kernel in SPICE can occur the values of ephemeris time are only as accurate as the currently published Cassini SCLOCK SPICE kernel. Spacecraft staring mode where staring = 0 when spinning and 1 otherwise INCA Images are organized as: Type ID: a 4 byte word characterized as: Byte 0 - Type: 0 = High Spatial, 1 = High Time, 2 = High m-TOF Byte 1 - Charge: 0 = Neutral, 1 = Ion Byte 2 - Species: 0 = H, 1 = He, 2 = CNO, 3 = Heavy, 4 = Other, 5 = All Byte 3 - TOF: 0 = Low, 1-6 = Medium, 7 = High Compression bits, Compression method, log compressed identifier Theta and Phi offsets from spacecraft coordinates The angle average and uncertainty are in units as image intensity in counts/(centimeters squared*steradian*seconds*keV) Each file contains all the species and tof combination image angle averages for one image resolution type. The resolution type, species and TOF values are included in the parameter set. INCA Browse Images -----------------The skymap browse images are in PNG files containing three rows by N columns of panels, where the bottom three rows are a continuation in time of the top three rows. Each row contains spin average high spatial ENA image skymaps (each one accumulated over four sectors), displayed for one species and TOF combinations. Row one contains the high TOF hydrogen images, row two contains the low TOF hydrogen images and row three contains the low TOF oxygen images. The energy range for each TOF range is shown to the right of each row. ENA images are collected when a high voltage is present on the INCA collimator. The value displayed is the log of the image intensity which is counts/(centimeters squared*steradian*seconds*keV). The color bars for each row are independent and are determined by the minimum and maximum pixels in that row (i.e., for the entire day). Each original image was 64 x 64 pixels and was transformed into the skymap frame, XINCA_BORESIGHT_CENTERED, which is described below in the coordinate system section. One days data is contained in one to three PNG files. The thumbnail browse images are in PNG files containing 1 up to 10 columns, high TOF browse ion thumbnail images displayed for seven TOF ranges (rows). Ion images are collected when no voltage is present on the INCA collimator. The image species include hydrogen at TOF ranges, where the energy range for each TOF range is shown to the right of each row. The value displayed is the log of the image intensity which is counts/(centimeters squared*steradian*seconds*keV). The color bars for each row are independent and are determined by the minimum and maximum pixels in that row (i.e., for the entire day). Each original image was 16 x 16 pixels and was transformed into the INCA azimuth and elevation frame, CASSINI_MIMI_INCA_LL, which is described below in the coordinate system section. One days data is contained in one to twenty-four PNG files. INCA ENA Movies ---------------The INCA ENA movies consist of MP4 movies displaying averaged ENA image skymaps (averaged over a variable, listed number of original on-board images), for one species and TOF combination. ENA images are collected when the voltage on the INCA collimator is high, typically 4kV. This excludes ions with E/q values less than ~180 to 200keV/q. The value displayed is the log of the image intensity in counts/(centimeters squared*steradian*seconds*keV). The INCA ENA images are only produced for interesting features in the INCA data and Titan flybys. The color bar limits are set to a common minimum and maximum value over the entire movie, chosen to bring out the salient features over the time covered. These values typically change from one movie to the next, based on activity levels and orbital position. Each original image N x N pixel image (where N is usually 32 or 64) was transformed into the Saturn frame, XINCA_SATURN_CENTERED, which is described in the coordinate system section below. For Titan flybys, the image was transformed into the Titan frame, XINCA_TITAN_CENTERED which is described in the coordinate system section below. Typically, though not always, the orbit of Titan, Dione and Rhea (dotted line), Titan center (dot), and the axis for Saturn equatorial system frame (white, centered at Saturn) are displayed. The definition of the Saturn equatorial system frame, is described in the coordinate system section below. The pink axis (when present) is the Saturn Kilometric Radiation frame. Due to the work of the RPWS team we now have several Saturn Kilometric Radiation frames available for use.[1] The SKR frame is also described below in the coordinate system section Ancillary Data ============== Coordinate System ================= The MIMI INCA display software makes primary use of three SPICE frames of reference which are used to display the images along with celestial bodies. These SPICE frames are provided in their MIMI SPICE analysis kernels set in the frame kernel. The skymap frame, XINCA_BORESIGHT_CENTERED, is a dynamically defined frame, defined as follows. The primary axis X is the INCA boresight axis. The secondary Z axis is the Z axis of the IAU_SATURN frame. The Y-axis completes the right-handed system. The skymap display is defined to display every frame with the Z axis up, X axis into the page and Y axis out to the left. So in the skymap, using this frame, Z or up is the spin axis of Saturn, into the page is the boresight. The Saturn frame, XINCA_SATURN_CENTERED, a frame dynamically defined as follows. The primary axis is the CASSINI spacecraft-to-Saturn vector and is labeled X. The secondary (Z) axis is the Z axis of the IAU_SATURN frame (the Saturn spin axis). The Y-axis completes the right-handed system. The Titan frame, XINCA_TITAN_CENTERED, a frame dynamically defined as follows. The primary axis is the CASSINI spacecraft-to-Titan vector and is labeled X. The secondary (Z) axis is the Z axis of the IAU_TITAN frame (the Titan spin axis). The Y-axis completes the right-handed system. The INCA Azimuth and elevation frame, CASSINI_MIMI_INCA_LL, is the primary axis X is the INCA boresight axis which goes into the page. The secondary Z axis is the Z axis of Cassini. The Y-axis completes the left-handed system. The definition of the Saturn equatorial system, SATURN_EQUITORIAL_SYSTEM, frame has the primary axis, labeled Z, parallel to the Saturn spin axis. The Y-axis is then defined as the cross product of this vector with the Saturn-Sun vector. The X-axis completes the right-handed system and is directed roughly sunward, lying in the plane containing both Z and the Saturn-sun vector. The MIMI INCA display software also displays the axis of Saturn using the Saturn Kilometric Radiation frame (SKR). Due to the work of the RPWS team we now have several Saturn Kilometric Radiation frames available for use.[1] The Z-axis is coincident with the instantaneous body rotation vector (spin axis) of Saturn. [1] A SLS4 Longitude system based on a tracking filter analysis of the rotation modulation of Saturn kilometric radiation. D.A. Gurnett, et. al. Software ======== There is IDL software provided on the MIMI web site, which will calibrate the INCA images conversion of count rates into flux. In addition, web applications are provided on the MIMI web site to display the INCA images in the skymap and thumbnail displays both singly and in multiple formats. Media/Format ============ These data are supplied to the Planetary Data System via electronic means and are then broken into segments based upon the media currently prescribed by PDS.

These data are available on-line from the Planetary Data System (PDS) at:

https://pds-ppi.igpp.ucla.edu/data/CO-S-MIMI-4-INCA-CALIB-V1.0/

Alternate Names

  • CO-S-MIMI-4-INCA-CALIB-V1.0

Discipline

  • Planetary Science: Fields and Particles

Additional Information

Spacecraft

Experiments

Questions and comments about this data collection can be directed to: Dr. Edwin V. Bell, II

 

Personnel

NameRoleOriginal AffiliationE-mail
Dr. Stamatios M. KrimigisData ProviderApplied Physics Laboratorytom.krimigis@jhuapl.edu
Mr. Martha Bolz KustererGeneral ContactApplied Physics Laboratorymartha_kusterer@jhuapl.edu
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