Data Set Information
DATA_SET_NAME MARINER 9 RSS DERIVED IONSPHERIC ELECTRON DENSITY PROFILES
DATA_SET_ID MR9-M-RSS-5-ELEDENPROFILES-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Overview ================== The Mariner 9 electron density profiles have been published graphically in [KLIORE1972A], [KLIORE1972B], [KLIOREETAL1973], [ZHANGETAL1990], and [KLIOREETAL1992]. They were archived as microfilmed data tables and images at the National Space Science Data Center (NSSDC) as dataset PSPA-00141, and this archive is described further at http://nssdc.gsfc.nasa.gov/nmc/datasetDisplay.do?id=PSPA-00141. We requested data tables and plots of ionospheric properties as functions of radial distance for all occultations for which ionospheric peak properties were reported in [KLIOREETAL1972B] and [KLIOREETAL1973]. We assumed that the absence of reported peak properties for a given occultation meant that no useful ionospheric profile was delivered to the archive. This approach primarily selected ingress occultations with solar zenith angles less than 90 degrees, although a handful of the selected occultations have solar zenith angles between 90 and 100 degrees. Neutral properties, although present in the archive and available to other interested researchers, were not deemed useful for our purposes. We provided a list of selected orbits to the NSSDC and subsequently received approximately 768 TIFF images of microfilmed information. The information in these images of data tables were processed using optical character recognition software, incorrectly recognized digits (which were legion) were manually corrected, and results were stored as ASCII tables. Quality control for each occultation was ensured by reproducing the accompanying electron density-radial distance plot and any similar plots in prior publications. This process generated an electron density-radius profile labeled by its orbit number for each available ingress occultation. For productive scientific analysis, additional supporting information is required. Tables in [KLIOREETAL1972B] and [KLIOREETAL1973] report latitude, longitude, solar zenith angle, peak electron density, peak radial distance, and peak altitude for each occultation. We verified that the peak electron densities and peak radial distances reported by [KLIOREETAL1972B] and [KLIOREETAL1973] are consistent with the recovered electron density profiles. Martian geodesy has evolved significantly since the Mariner era, so the published latitudes, longitudes, and peak altitudes need careful consideration. Generally speaking, pre-Mars Global Surveyor work tended to use areographic latitudes and post-Mars Global Surveyor work has tended to spherical planet, which leads to areocentric latitudes. Since the difference between latitudes defined with these two conventions is in any case always less than 1 degree, we have interpreted the reported latitudes as modern-era areocentric values [SMITHETAL2001]. Longitudes in [KLIOREETAL1972B] and [KLIOREETAL1973] are west longitudes, which were converted into east longitudes by subtracting them from 360 degrees. Tracking the many different reference areoids used over the past four decades to convert radial distance to altitude is a major undertaking, which we sidestepped by converting each occultation's list of of radial distances into altitudes using the radius of the MOLA areoid at the appropriate latitude and longitude [SMITHETAL2001]. The end product is a set of 114 electron density profiles as functions of radial distance and altitude, each accompanied by orbit number, date, latitude, longitude, solar zenith angle, radius of areoid, radial distance to maximum electron density, altitude of maximum altitude density, and maximum electron density. Electron density uncertainties were neither archived nor discussed extensively in publications from the Mariner 9 era, but they can be estimated for each profile as the smallest value in that profile. 78 profiles were acquired during the primary mission on orbits 1-79 and 36 profiles were acquired during the extended mission on orbits 352-450. In the primary mission, profiles typically spanned 80 to 300 km with a vertical resolution of 2 km and a lowest reported density of 700 cm^-3. In the extended mission, profiles typically spanned 80 to 240 km with a vertical resolution of 1 km and a lowest reported density of 1200 cm^-3. Point-to-point fluctuations in electron density are noticeably greater in the profiles from the extended mission than in those of the primary mission. The high gain antenna was not pointed at Earth during extended mission occultations, which reduced the signal-to-noise ratio of the experiments [KLIOREETAL1973]. Parameters ========== Each .TAB file in the ANC/ directory contains the following items. Orbit number ORBIT NUMBER Date of occultation, UTC DATE Latitude of occultation, degrees north LATITUDE Longitude of occultation, degrees east EAST_LONGITUDE Solar zenith angle of occultation, deg SOLAR_ZENITH_ANGLE Radius of areoid at LATITUDE and EAST_LONGITUDE, km RADIUS_OF_AREOID Radial distance to maximum electron density, km R_NMAX Altitude of maximum electron density, km Z_NMAX Maximum electron density, number per cubic centimeter NMAX Each .TAB file in the EDS/ directory contains the following items: Radial distance, km RADIAL DISTANCE Altitude, km ALTITUDE Electron density, number per CC ELECTRON_DENSITY The altitude is defined relative to an areoid produced by the Mars Orbiter Laser Altimeter instrument on Mars Global Surveyor [SMITHETAL2001]. Uncertainties in these parameters are not specified precisely. Uncertainties in electron density can be estimated for each profile as the smallest value in that profile. In the primary mission, the typical lowest reported density was 700 cm^-3, and in the extended mission, the typical lowest reported density was 1200 cm^-3. Timing ====== Precise timing information is not readily available for these profiles, although it could perhaps be provided by a diligent investigation of the relevant SPICE kernels (http://naif.jpl.nasa.gov/pub/naif/M9/kernels/). We assigned dates to each occultation based on day of year information written on the microfilmed tables. Data Processing =============== Data processing is described in the documents listed in the REF.CAT file and references therein.
DATA_SET_RELEASE_DATE 2015-10-15T00:00:00.000Z
START_TIME 1965-01-01T12:00:00.000Z
STOP_TIME N/A (ongoing)
MISSION_NAME MARINER69
MISSION_START_DATE
MISSION_STOP_DATE
TARGET_NAME MARS
TARGET_TYPE PLANET
INSTRUMENT_HOST_ID MR9
INSTRUMENT_NAME RADIO SCIENCE SUBSYSTEM
GRAVITY SCIENCE INSTRUMENT
INSTRUMENT_ID RSS
INSTRUMENT_TYPE RADIO SCIENCE
NODE_NAME planetary plasma interactions
ARCHIVE_STATUS PRE PEER REVIEW
CONFIDENCE_LEVEL_NOTE Data Coverage and Quality ========================= Given the small number of available occultations, data coverage is limited. No gaps have been identified in individual profiles. Uncertainties in the ionospheric electron densities are not known precisely, as discussed above. Limitations and Caveats ======================= These data products come a spacecraft whose operations ended over 40 years ago. Therefore the documentation and other aspects of the dataset are not as complete as would be expected for a current NASA mission. Nevertheless, it is felt that archiving the dataset in its current state, thereby preserving it for posterity, is better than risking that it be lostirrevocably.
CITATION_DESCRIPTION P. Withers, S. Joy, MARINER 9 RSS DERIVED IONSPHERIC ELECTRON DENSITY PROFILES, MR9-M-RSS-5-ELEDENPROFILES-V1.0, NASA Planetary Data System, 2014.
ABSTRACT_TEXT This dataset contains 114 ionospheric electron density profiles (EDS files) derived from Mariner 9 radio occultation data.
PRODUCER_FULL_NAME PAUL WITHERS
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