Data Set Information
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| DATA_SET_NAME |
MESSENGER E/V/H MASCS 3 UVVS CALIBRATED DATA V1.0
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| DATA_SET_ID |
MESS-E/V/H-MASCS-3-UVVS-CDR-CALDATA-V1.0
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| NSSDC_DATA_SET_ID |
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| DATA_SET_TERSE_DESCRIPTION |
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| DATA_SET_DESCRIPTION |
Data Set Overview : This data set consists of the MESSENGER MASCS UVVS calibrated data records (CDRs). The UVVS experiment is equipped with three photomultiplier tubes, which are sensitive to three different wavelength ranges. Resulting spectra cover the wavelength ranges of the far ultraviolet (FUV)(115-190 nm), middle ultraviolet (MUV) (160-320 nm), and visible (VIS) (250-600 nm), with a resolution of 0.5 nm for the FUV channel, 0.7 nm for the MUV channel, and 0.6 nm for the VIS channel. There is a data overlap with VIRS in the VIS wavelength range. There are four standard UVVS data products: FUV data, MUV data, VIS data, and Housekeeping data. The housekeeping EDR contains instrument parameters that may be useful in analyzing the UVVS data. Housekeeping data are incorporated into the three standard CDR data products (one each for FUV, MUV, VIS). Each CDR product is comprised of a Header (HDR) file, showing the instrument command parameters for a given observation, and a Science (SCI) file showing counts, science data at various stages of calibration, and pointing information for each step of an observation. Instrument Overview : The MASCS instrument consists of a small Cassegrain telescope that simultaneously feeds the UVVS and VIRS experiments. The MASCS UVVS experiment is a scanning grating monochromator equipped with three photomultiplier tubes, providing spectral information in the far ultraviolet (115-190 nm), middle ultraviolet (160-320 nm), and visible (250-600 nm) wavelength ranges. The UVVS detector will help determine the global composition and structure of Mercury's exosphere by measuring emission from known species as well as search for new ones. See the INST.CAT file for more information and [MCCLINTOCK&LANK2007] for full details. Parameters : The principal parameters when observing with the MASCS UVVS are as follows: * Start Position: The start position where the grating drive begins a scan. * Step Size: The step size in units of grating step. One grating step is equal to one arcmin. The wavelength delta of a single UVVS grating step is detector dependent. Wavelength and sensitivity tables are provided in the UVVS_EDR2CDR.TXT document, and the equations describing step wavelengths are provided in the MASCS_CAL_RPT.PDF document. These documents are located in the DOCUMENT directory. * Step Count: The number of steps the grating drive will take in a scan. The Step Count multiplied by the Step Size relates to the range of wavelengths that will be observed in one UVVS observation. * Integration Time: Integration time in grating drive loop control interrupt periods (nominally 3000 Hz). * Step Time: The step time in the grating drive loop control interrupt periods (nominally 3000 Hz). * Phase Offset: The phase offset between the beginning of the grating drive step and the start of a PMT integration in units of 0.3 milliseconds. Default value is 0 (no phase offset). By setting the phase offset to a non-zero value (reserved for contingency operations), the user will tell the software to initiate a step before the end of an integration, accounting for latencies in the motor controller. * Number of Scan Cycles: The number of times to repeat a scan. * Zigzag Option: Indicates whether grating drive moves in a 'triangle' (stepping up, then stepping down), or 'sawtooth' (stepping up, then 'flying' down) motion. A 'triangle' observation takes one grating scan stepping up the grating, then reverses direction and takes the next grating scan stepping back down the grating. Scans in opposite directions are offset from one another by two grating step positions such that the wavelength ranges are slightly different. A 'sawtooth' observation takes one grating scan stepping up the grating, then 'flies' the grating back to the START_POSITION to take the next observation. * Compression: Selects between 16 bit data (uncompressed) or 9 bit data (compressed). * Slit Mask Position: Indicates whether the slit mask is in the atmospheric (open) or surface (closed) position. Atmospheric slit results in a 1 deg. by 0.04 deg. instantaneous field of view (iFOV). Surface slit results in a 0.05 deg. by 0.04 deg. iFOV. * FUV On: Select if the far ultraviolet photomultiplier tube is powered on or off. * MUV On: Select if the middle ultraviolet photomultiplier tube is powered on or off. * VIS On: Select if the visible photomultiplier tube is powered on or off. Calibration Overview : This data set consists of calibrated data derived from MASCS UVVS Experimental Data Records (EDR). The Science EDRs are the raw data records used to derive emission and reflectance data used for scientific analysis. The Science EDRs contain raw counts of the UVVS photomultiplier tubes (PMT) at the commanded step of the UVVS grating, which corresponds to a specific wavelength of light. Wavelength range and sensitivity of each PMT at each grating step vary, as documented in the MASCS Calibration Report, MASCS_CAL_RPT.PDF, provided in the DOCUMENT directory. Before the science data can be used for scientific analysis, the count rates in the EDRs must be converted to physical units and the data must be transformed into meaningful physical reference systems. This conversion yields calibrated data which are stored in Calibrated Data Records (CDRs). The processing steps from the EDR to the CDR level include: 1. Determine wavelength and timing for each step of a given grating scan observation. 2. Correct for PMT nonlinearity. 3. Account for zig-zag scans if observation uses grating zig-zag. 4. Apply empirical PMT temperature correction to dark counts. 5. Remove solar scattering where possible. 6. Apply PMT sensitivity for every step of every observation, convert counts to radiance at sensor. 7. Determine pointing parameters (geometry fields calculated from SPICE) for every step of every observation. Surface pointing parameters are determined relative to the Mercury DEM. 8. Assign data quality flags and indicators. The processing steps are detailed in the documents UVVS_CDR_DDR_SIS.PDF and UVVS_EDR2CDR.TXT, located in the DOCUMENT directory. Calibration Updates Observations of Spica and Sirius by the UVVS are used to correct errors in the ground calibration for FUV, MUV and VIS channels. Motivated by differences we see in our observations compared to observations of Spica with the UVS on the Venus Express mission, a more careful analysis of the original Spica data was performed in September 2013. The result is a small adjustment (~15%) to the radiometric sensitivity of the short wavelength portion of the FUV channel. The adjustment to the FUV channel was included in PDS delivery 11. In December 2016, the calibration for all three channels was reevaluated using stellar data over the orbital phase. The sensitivity of all the channels decreased over the orbit phase of the mission. A time-dependent correction was applied to all the channels with the maximum correction at the end of the mission. VIS channel: a maximum 5% adjustment was applied. MUV channel: a maximum 15% adjustment was applied to wavelengths <300nm and a maximum 5% adjustment for wavelengths >300nm. FUV channel: a maximum 30% adjustment was applied to wavelengths <125nm and a maximum 20% adjustment for wavelengths >125nm. This sensitivity adjustment was included in PDS delivery 16. Coordinate Systems : MASCS UVVS data are represented in the following coordinate systems: * Planetocentric body fixed: The MBF coordinate system is defined by the planetocentric position, Cartesian X, Y, Z coordinates related to the planetocentric distance, latitude measured positive northward from the equator, and longitude measured positive eastward from the prime meridian. * Cartographic: Surface observations use IAU planetocentric system with East longitudes being positive for planetary surfaces. The IAU2000 reference system for cartographic coordinates and rotational elements was used for computing latitude and longitude coordinates of planets. Data : There are three UVVS CDR data products, one for each detector (FUV, MUV, VIS). Data from the MASCS housekeeping EDR product generated by the MASCS instrument, which is the same for both the UVVS and VIRS components of the MASCS experiment, are incorporated into the CDRs. The CDR for one of the three detectors consists of two files. The Header file (HDR) contains values for the instrument command parameters set that apply for the entirety of the observation encapsulated by the CDR. The Science file (SCI) data are the counts accumulated by the photomultiplier tube at a given position of the grating, in the order that the counts were collected. By using the values of the specific observing parameters that are related to the grating start position, number of grating steps, pattern of grating steps, and number of scans, each grating position can be determined and mapped to a specific wavelength. All other per-step information on counts, calibrated data, spacecraft time and orientation, target location, and other pointing parameters, are kept in the Science file. A separate CDR is created for each commanded scan set of one of the three detectors. Due to power considerations, a maximum of two photomultiplier tubes may record data at any given time; if two detectors acquire data simultaneously, two separate CDRs are still created. Data for the three UVVS detectors of the FUV, MUV, and VIS are always in separate EDRs.
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| DATA_SET_RELEASE_DATE |
2017-05-12T00:00:00.000Z
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| START_TIME |
2004-08-27T10:06:46.000Z
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| STOP_TIME |
2015-04-30T03:03:45.000Z
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| MISSION_NAME |
MESSENGER
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| MISSION_START_DATE |
2004-08-03T12:00:00.000Z
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| MISSION_STOP_DATE |
2015-04-30T12:00:00.000Z
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| TARGET_NAME |
EARTH
VENUS
CALIBRATION
MERCURY
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| TARGET_TYPE |
PLANET
CALIBRATION
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| INSTRUMENT_HOST_ID |
MESS
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| INSTRUMENT_NAME |
MERCURY ATMOSPHERIC AND SURFACE COMPOSITION SPECTROMETER
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| INSTRUMENT_ID |
MASCS
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| INSTRUMENT_TYPE |
VISIBLE/INFRARED SPECTROGRAPH
UV/VISIBLE SPECTROMETER
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| NODE_NAME |
Geosciences
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| ARCHIVE_STATUS |
ARCHIVED - ACCUMULATING
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| CONFIDENCE_LEVEL_NOTE |
Confidence Level Overview : The MASCS UVVS Calibrated Data Record (CDR) data released for the UVVS consists of the calibrated data converted to physical units and represented in physical coordinate systems. Data presented here are an accurate representation of the UVVS data as received from the spacecraft, and reflect the processing steps from the MASCS UVVS Experimental Data Records (EDRs) to CDR level detailed in the document UVVS_EDR2CDR.TXT located in the DOCUMENT directory. The UTC and MET time tags have been corrected for timing latencies in the instrument so that the UTC and MET correspond to the physical time of the observation. Review : The UVVS CDR was reviewed internally by the MASCS team prior to release to the PDS. PDS also performed an external review of the MASCS UVVS CDRs (FUV, MUV and VIS photomultiplier tube (PMT) data each have separate CDR types). Data Coverage and Quality : Data reported are the calibrated data received from the spacecraft during the mission phases: Launch, Earth Cruise, Earth Flyby, Venus 1 Cruise, Venus 1 Flyby, Venus 2 Cruise, Venus 2 Flyby, Mercury 1 Cruise, Mercury 1 Flyby, Mercury 2 Cruise, Mercury 2 Flyby, Mercury 3 Cruise, Mercury 3 Flyby, Mercury 4 Cruise, Mercury Orbit, Mercury Orbit Year 2, Mercury Orbit Year 3, Mercury Orbit Year 4, and Mercury Orbit Year 5. These mission phases are defined as: Start time End time Phase Name Date (DOY) Date (DOY) ----------------- ----------------- ----------------- Launch 03 Aug 2004 (216) 12 Sep 2004 (256) Earth Cruise 13 Sep 2004 (257) 18 Jul 2005 (199) Earth Flyby 19 Jul 2005 (200) 16 Aug 2005 (228) Venus 1 Cruise 17 Aug 2005 (229) 09 Oct 2006 (282) Venus 1 Flyby 10 Oct 2006 (283) 07 Nov 2006 (311) Venus 2 Cruise 08 Nov 2006 (312) 22 May 2007 (142) Venus 2 Flyby 23 May 2007 (143) 20 Jun 2007 (171) Mercury 1 Cruise 21 Jun 2007 (172) 30 Dec 2007 (364) Mercury 1 Flyby 31 Dec 2007 (365) 28 Jan 2008 (028) Mercury 2 Cruise 29 Jan 2008 (029) 21 Sep 2008 (265) Mercury 2 Flyby 22 Sep 2008 (266) 20 Oct 2008 (294) Mercury 3 Cruise 21 Oct 2008 (295) 15 Sep 2009 (258) Mercury 3 Flyby 16 Sep 2009 (259) 14 Oct 2009 (287) Mercury 4 Cruise 15 Oct 2009 (288) 03 Mar 2011 (062) Mercury Orbit 04 Mar 2011 (063) 17 Mar 2012 (077) Mercury Orbit Year 2 18 Mar 2012 (078) 17 Mar 2013 (076) Mercury Orbit Year 3 18 Mar 2013 (077) 17 Mar 2014 (076) Mercury Orbit Year 4 18 Mar 2014 (077) 17 Mar 2015 (076) Mercury Orbit Year 5 18 Mar 2015 (077) 30 Apr 2015 (120) To validate the initial CDR dataset, the MASCS team did the following: * Examined the Mercury 1 flyby dataset from Jan 14 2008 in detail. These were the most scientifically significant observations that had been made at the time of initial validation. - Checked all data columns for format and sanity numbers - Compared calibration numbers for earlier independent analysis before CDR development - Compared pointing information (vectors, lats, lons, distances, angles) to previous independent solutions * Spot checked additional data sets preceding Mercury 1 flyby. The orbital CDR dataset is evaluated on an ongoing basis, checking for completeness and data integrity. MASCS UVVS data were collected during all phases except Venus 1 Flyby. During these planned operational periods, the UVVS functioned nominally and the data quality was good. Additional numbered notes added as necessary. This is a high-level presentation of CDR validation. Lower level CDR details, including, e.g. SBOS trips, temperature alarms, and footprints on/off planet are best obtained through the Data Quality Index (DQI) of the UVVS CDR. Specific MASCS operational periods were: Start time End time Phase Name Date (DOY) Date (DOY) Operations -------------------- ----------------- ----------------- ------------ Launch 03 Aug 2004 (216) 12 Sep 2004 (256) Checkout Earth Cruise 13 Sep 2004 (257) 18 Jul 2005 (199) Starcals (1), Cover Open Earth Flyby 19 Jul 2005 (200) 16 Aug 2005 (228) Earth/Moon (2) Venus 1 Cruise 17 Aug 2005 (229) 09 Oct 2006 (282) Starcals Venus 1 Flyby 10 Oct 2006 (283) 07 Nov 2006 (311) n/a Venus 2 Cruise 08 Nov 2006 (312) 22 May 2007 (142) Starcals (3,4), Venus, Operation Tests Venus 2 Flyby 23 May 2007 (143) 20 Jun 2007 (171) Venus (5) Mercury 1 Cruise 21 Jun 2007 (172) 30 Dec 2007 (364) Starcals (6), Operation Tests Mercury 1 Flyby 31 Dec 2007 (365) 28 Jan 2008 (28) Mercury (7), Lyman Alpha Mercury 2 Cruise 29 Jan 2008 (029) 21 Sep 2008 (265) Starcals, Operation Tests Mercury 2 Flyby 22 Sep 2008 (266) 20 Oct 2008 (294) Mercury, Lyman Alpha Mercury 3 Cruise 21 Oct 2008 (295) 15 Sep 2009 (258) Starcals (8), Venus Mercury 3 Flyby 16 Sep 2009 (259) 14 Oct 2009 (287) Mercury (9), Lyman Alpha Mercury 4 Cruise 15 Oct 2009 (288) 03 Mar 2011 (062) (10), Starcals, Venus, Operation Tests Mercury Orbit 04 Mar 2011 (063) 17 Mar 2012 (077) Mercury (11-13), Starcals, Venus Mercury Orbit Year 2 18 Mar 2012 (078) 17 Mar 2013 (076) Mercury (14-16), Starcals, Venus Mercury Orbit Year 3 18 Mar 2013 (077) 17 Mar 2014 (076) Mercury (17-18), Starcals, Venus Mercury Orbit Year 4 18 Mar 2014 (077) 17 Mar 2015 (076) Mercury (19), Comet Encke, Comet ISON, Comet Oukaimeden, Starcals, Venus Mercury Orbit Year 5 18 Mar 2015 (077) 30 Apr 2015 (120) Mercury (20-21) Notes: (1) Starcals before June 2005 viewed through cover window. (2) UVVS command errors in corona scans reduced number of scans executed by ~1/2. SBOS trips at moon stopped UVVS VIS-PMT data as expected. 10 missing MUV packets at this time. (3) One starcal missed target due to star tracker error. (4) Test and switch over to macro-based commanding of UVVS. (5) SBOS trips at Venus stopped green line scan. (6) S/C event during starcal; instrument turned off during starcal. (7) UVVS grating offset affected data during first Mercury flyby. The offset was 5 grating steps. CDR data during this time period were affected in that the range of wavelengths actually measured is different from the nominal range and spectra were shifted to longer wavelengths. A correction for this effect has been applied in the final calibration (detailed in the file UVVS_PROCESSING_UPDATES_PDS16.PDF in the DOCUMENT directory), so calibrated data in this time range are usable, but they may reflect higher uncertainties given the additional processing required. The formal list of times affected by this offset is noted in the file UVVS_GRATING_OFFSET.TAB found in the CALIB directory. (8) Pointing error during May 2009 starcal; star not observed. (9) Flyby anomaly - no data after Mercury Closest Approach until post-flyby Mercury-as-star observations. (10) Missing packet in Dec 2010 turn-on sequence. Missing packets (5 second observations) noted in some H Lyman alpha scans, possibly simply timing cutoffs; no data quality compromise. (11) Some dates affected by coronal mass ejections (CMEs). See complete list below. (12) On 20110430 - UVVS inadvertently looked at sunlit planet, triggering SBOS trips. (13) Single Event Upsets (SEUs): 11250 X-Class solar flare 12064 EEPROM hit lost a few days of data (14) Some dates affected by CMEs; see list below. (15) UVVS grating offset affected data during March and April 2012. The offset was 5 grating steps. See note #7 above for description of effects. (16) Switch from 12-hour orbit to 8-hour orbit causes unusually large gap in data collection. (17) Some dates affected by CMEs; see list below. (18) UVVS grating offset affected data from September 5 through November 22, 2013. The offset was 5 grating steps. See note #7 above for description of effects. (19) Some dates affected by CMEs; see list below. (20) Some dates affected by CMEs; see list below. (21) Temperature Fault protection software disabled during final days in orbit. Final list of dates during which the UVVS detectors were affected by CMEs or other solar events. These events generally result in elevated background levels in the UVVS which can take some time (days) to return to normal. It is **STRONGLY** recommended that data from these dates not be used in science analysis. Dates on which MASCS data are affected by CMEs/solar events: 06-05-2011 06-06-2011 06-07-2011 09-20-2012 09-21-2012 04-24-2013 04-25-2013 08-20-2013 08-21-2013 09-01-2014 09-02-2014 09-03-2014 09-04-2014 12-04-2014 12-13-2014 12-14-2014 12-15-2014 12-16-2014 03-24-2015 Final list of dates during which the UVVS detectors were adversely affected by instrumental or scheduling issues: 01-01-2008 through 01-31-2008 (see note #7 above) 03-05-2012 through 03-29-2012 (see note #16 above) 03-30-2012 through 04-23-2012 (see note #15 above) 09-05-2013 through 11-22-2013 (see note #18 above) Cruise operations/observations have additional details in the Master Cruise Table (a Microsoft Excel file) in the Extras directory. There are slightly fewer UVVS Science CDRs because there were a few EDRs that contained no data at all, just header information (i.e. loop was begun, but halted by normal macro operations before data were taken.) Some Visible Detector CDRs (labels beginning with UVC) that have step wavelength values greater that 250 nm may have erroneous values for the field entries listed below. The user can identify these by inspecting the value in item 42. If the dark_rate is greater than 100, then the entries should be considered unreliable. 42. DARK_RATE 43. SCATTERED_LIGHT_RATE 44. FULLY_CORRECTED_COUNT_RATE 45. FULLY_CORRECTED_COUNT_RATE_UNCERTAINTY 46. STEP_RADIANCE_KR 47. STEP_RADIANCE_W 48. STEP_RADIANCE_SIGNAL_TO_NOISE 49. PMT_TEMPERATURE Values in the data quality index are unreliable in this version of the data released through the PDS. Limitations : This data set is calibrated data. The data are received from the spacecraft telemetry and ingested into the MESSENGER Science Operations Center (SOC), then run through the MASCS calibration pipeline. No data uncharacterized gaps have been identified for any of the MASCS operational periods. An independent derivation of the Release 4 UVVS CDR geometry fields revealed a few discrepancies greater than 0.1 percent, which we note here. Each component of the vector 'PLANET_SC_VECTOR_J2' was found to be smaller than the CDR values by 0.5 percent. The y-components of the vector 'PLANET_SUN_VECTOR_TG' and 'SUN_POSITION_VECTOR_TG' were found to be smaller than the CDR values by 0.4 percent. The data have been calibrated to the best possible level; however, there are both particle-induced effects due to solar events and temperature-dependent effects in the background removal and wavelength calibration that are being evaluated on an ongoing basis. The user is warned that these effects will sometimes result in false positives in the calibrated radiance (i.e., false detections). Care should be exercised in using the CDR data, particularly when results are anomalous in appearance, but the erroneous measurements are not always obvious. These issues are significantly less of a problem in the DDR products (but not entirely eliminated), which have been scrubbed to a higher level of confidence. Users are **STRONGLY ENCOURAGED** to use the DDR data for scientific analysis.
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| CITATION_DESCRIPTION |
Izenberg, N., MESSENGER E/V/H MASCS 3 UVVS CALIBRATED DATA V1.0, MESS-E/V/H-MASCS-3-UVVS-CDR-CALDATA-V1.0, NASA Planetary Data System, 2008.
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| ABSTRACT_TEXT |
Abstract : This data set consists of the MESSENGER MASCS UVVS calibrated observations, also known as CDRs. The MASCS UVVS experiment is a scanning grating monochromator equipped with three photomultiplier tubes. There are three UVVS CDR data products, one for each detector, which cover the wavelength ranges of the far ultraviolet (FUV), middle ultraviolet (MUV), and visible (VIS).
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| PRODUCER_FULL_NAME |
NOAM IZENBERG
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| SEARCH/ACCESS DATA |
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Mercury Orbital Data Explorer
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