Frequently Asked Questions: Planetary


This FAQ is not intended to answer general questions about planetary probes or information about solar system bodies. These FAQs (for the sci.space newsgroups on usenet) are available at The Internet FAQ Archive.
URL: http://www.faqs.org/faqs/space/

This FAQ is intended to address questions which NSSDCA personnel are called on to answer.


Contents


How is this FAQ organized?

As much as possible, it is organized by solar system object as one progresses outward from the Sun. For each object, there may be some questions which may be specific to only one planetary mission which has visited that object as well as those which are pertinent to the object in general. In those cases, there are subheadings under the object to specify whether the question is a general (not mission specific) or mission-related question.

In some cases, a given question may apply to the data from more than one object (for example, because a mission went to several planets/objects) or is a more generic questions (for example, about planetary geology or atmospheres). Answers to these questions may be found under the General category at the top of the FAQ.


General

  1. Where can I find images of the comet P/Shoemaker-Levy 9 collision with Jupiter on-line?

    A large (and growing) number of sites have these images. A set of over 200 images and links to many other sites is available on NSSDCA's Comet Impact page.
    URL: http://nssdc.gsfc.nasa.gov/sl9/comet_images.html

  2. Where can I find images of the Moon and planets on-line?

    There are a number of places, both in and outside of NASA, where such images are available. Therefore, a comprehensive listing of such sites is neither possible or practical. However, there are some places worth pointing out.

    The first such site is NSSDCA's Photo Gallery, a service available from NSSDCA for WWW users. The gallery shows a number of images (including non-planetary images) produced with data available from NSSDCA's archives and other sources. The collection of photos is growing, so keep an eye out for new additions.
    URL: http://nssdc.gsfc.nasa.gov/photo_gallery/

    Another site at NSSDCA is the Catalog of Spaceborne Imaging. This service contains exclusively planetary images and will hopefully eventually contain all of NSSDCA's plantary imaging in digital format.
    URL: http://nssdc.gsfc.nasa.gov/imgcat/

    A list of other sites where one might find lunar and planetary images of interest is also available.
    URL: http://nssdc.gsfc.nasa.gov/photo_gallery/other_sites.html

  3. What do the file names for the images and directories on the Voyager CD-ROMs mean?

    On the Voyager imaging CD-ROMs, the top level directories indicate the object name, for example Jupiter, Saturn, Rings, Oberon. Under that lies directories with names like CnnnnXXX and, under each of these directories, lie images with names like Cnnnnmmm. These file names are derived from the actual exposure numbers, which are of the form xxxxx.yy. For the Voyager Imaging Science Subsystem (ISS), each exposure is tagged with the current spacecraft clock time. Because the spacecraft clock time is measured in seconds from launch, the number is quite large and gets larger as time goes by. Rather than having to deal with extraordinarily large numbers, the time is reduced in two ways to come up with the exposure number. First, the time is taken modulo 65,536 (16 bit) to come up with the first five digits of the exposure number (which, padded appropriately with zeros on the left becomes the xxxxx part). Second, the time is taken modulo 60 to come up with the last two digits of the number (the yy part). From the exposure number xxxxx.yy, one takes the first four digits and sets them equal to the nnnn portion of the directory. For the image names, one just elimates the decimal place. For example, the image 8966.31 can be found in the directory C0896XXX as file C0896631.IMG.

  4. What do the file names for the images and directories on the Galileo CD-ROMs mean?

    On the Galileo imaging CD-ROMs containing raw data, each of the images is placed into top level directories indicating the object name, for example Venus, Earth, Calibration, etc. Under that lies directories with names of the form Cnnnnnn and in each of those, images with names of the form xxxxR. These names are derived from the spacecraft clock time. Because the spacecraft clock time is measured in seconds (down to fractions of a second) from launch, the number is quite large and gets larger as time goes by. Because there are approximately 30 million seconds in a year and the mission is expected to last through 1997 at least, the file names could get quite big. Rather than do this, the last two digits of the spacecraft clock time and the first two places to the right of the decimal in the spacecraft clock time are used to make up the file name; the R on the end indicates it is "raw" (i.e., unprocessed) data. The directory names are then obtained by dividing the spacecraft clock time by 100 and eliminating the decimal places. If necessary, the number is padded at the beginning with zeros so that six numbers are present in the name. For example, an image taken at 00180626.00 spacecraft clock time becomes image number 2600R on directory C001806.

  5. What is all this I hear about an upcoming planetary alignment? What effect will this have on the Earth and how frequently do these things occur?

    The planets Mercury, Venus, Earth, Mars, Jupiter, and Saturn will be more or less lined up on 5 May 2000. There will be no observable physical effect on the Earth from this alignment. Depending on how strictly you want to define "alignment", the inner six planets line up every few hundred years or so. For more information, see the planetary alignment page.


Mercury

  1. Does NSSDCA have Mariner 10 Mercury flyby data on CD-ROM?

    No, the Mariner 10 imaging data as well as the fields and particles measurements have not yet had CD-ROMs produced. Both kinds of data are available, however, on 9-track magnetic tape. Photographs of Mercury are also available.

    More information on CD-ROMs available from the NSSDCA can be found in the NSSDCA CD-ROM Catalog.
    URL: http://nssdc.gsfc.nasa.gov/cd-rom/

  2. Does NSSDCA have Digital Image/Terrain/Elevation Models/Maps for Mercury?

    No. The Astrogeology Branch of the United States Geological Survey in Flagstaff, Arizona, which produces such things, has not indicated that such a product is forthcoming. They should be contacted for further information.


Venus

Pioneer Venus

  1. Does NSSDCA have PVO data on CD-ROM?

    Some preliminary gravity and radar data were archived on the Pre-Magellan CD-ROM to support Magellan activities, but complete sets of these data on CD-ROM have not yet been produced.

    Data on CD-ROM from some of the particles and fields experiments on the Pioneer Venus Orbiter are currently being produced by the Planetary Data System's Planetary Plasma Interactions (PPI) node. The first set of CD-ROMs contains 24 s and high-resolution data from the magnetometer (OMAG) and electric field detector (OEFD) experiments on the orbiter as well as ephemeris data. Once this set is completed (about 55-60 volumes), other fields and particles experiments will begin to arrive on separate CD-ROM series.

    More information on CD-ROMs available from the NSSDCA can be found in the NSSDCA CD-ROM Catalog.
    URL: http://nssdc.gsfc.nasa.gov/cd-rom/

  2. Does NSSDCA have digital image models (DIMs) of Venus?

    Yes, in the form of the Magellan C3-MIDRs. These are sinusoidal equal area projections of compressed Magellan radar images, and are available on the Magellan CD-ROMs (NSSDCA Data Set PSPG-00175). More information on these DIMs and DIMs of other planets and satellites is available on the Digital Image Models Page.
    URL: http://nssdc.gsfc.nasa.gov/planetary/dims.html

Magellan

  1. What is meant by "Cycle 1" data?

    The Magellan project for convenience divided up the observing periods for Magellan delineated by the time it took the orbiter to cover 360 degrees of longitude. This time is equal to the sidereal day of Venus, ~243 Earth days, or roughly eight months. Magellan arrived at Venus in mid-August 1990 and, due to normal spacecraft and instrument checkout activities as well as initial problems with communications, cycle 1 began officially on 15 September 1990 and lasted until 15 May 1991.

  2. What kind of observations were made by Magellan during the various cycles?

    During the first three cycles, Magellan made primarily radar, altimeter, and radiometer observations of Venus' surface. Subsequent cycles were dedicated primarily to gravimetric observations. The orbit was circularized by aerobraking between cycles 4 and 5. Other kinds of observations (solar corona, atmospheric, etc.) were also made during some of these cycles.

  3. What exactly are Magellan F-BIDRs, F-MIDRs and C-MIDRs?

    Magellan raw Synthetic Aperture Radar (SAR) data is processed to create Basic Image Data Records or BIDRs. F-BIDRs are simply Full-resolution (~75 m/pixel) Basic Image Data Records, which look like long, thin strips of radar imagery, representing one pass of the Magellan spacecraft. These are difficult to use for geologic interpretation because they are only about 20 Km wide by 17,000 Km long, so a mosaic of these images is produced, a Full-resolution Mosaicked Image Data Record, or F-MIDR.

    The F-MIDRs are high resolution radar "pictures" of the surface of Venus. An F-MIDR has the same resolution as the F-BIDRs (~75 m/pixel), but covers an area approximately 5 degrees on a side. (One degree on Venus is approximately 105 Km at the equator.) These F-MIDRs have been compressed (an averaging of 9 pixels down to one) to form lower resolution but larger area Compressed Mosaicked Image Data Records or C-MIDRs. Three levels of compression have been done: Compressed once (C1-MIDRs), 15 degrees on a side and 225 m resolution; Compressed twice (C2-MIDRs), 45 degrees on a side and 675 m resolution; and, Compressed thrice (C3-MIDR's), 120 by 80 degrees and 2025 m resolution.

    There are also products called Polar Mosaicked Image Data Records, or P-MIDRs, which cover from 80 degrees latitude to the pole.

  4. What do the numbers on the MIDRs indicate?

    Each MIDR has an identification number of the form t-MIDR.xxHyyy;C, where t is the data type: F, C1, C2, or C3; xx is the approximate latitude of the center of the mosaic, H is the hemisphere (N or S); yyy is the approximate longitude of the center of the mosaic; and C gives the cycle and version number. For cycle 1, C is a one digit number giving the version number. For cycles 2 and 3, C is a three digit number, with the first digit being the cycle number and the last the version number. For example, F-MIDR.15S140;301 is a full-resolution mosaicked image data record, centered at 15 degrees south latitude and 140 degrees longitude, from the third data cycle, version 1.


Earth

  1. Are any of the images of the Earth taken by planetary probes available on CD-ROM?

    Images of the Earth from the Galileo spacecraft as Raw Experimenter Data Records (REDRs) are available for the first Earth flyby, which occurred in late 1990. This CD-ROM set will eventually include all of the Galileo cruise phase imaging (all images from the Solid-State Imager prior to Galileo's main mission at Jupiter), including those of Venus, the Earth, the Moon, and the asteroids Gaspra and Ida. The data for the Earth-2 flyby have recently arrived (Feb. 1995) and are now available.

    More information on CD-ROMs available from the NSSDCA can be found in the NSSDCA CD-ROM Catalog.
    URL: http://nssdc.gsfc.nasa.gov/cd-rom/

  2. What about Earth Science data taken by Earth orbiters?

    Earth science data is slowly being transitioned out from NSSDCA, although some data are still available. Check the Earth Science Data in Transition Page for more information.


Moon

  1. Are there lunar images available on CD-ROM?

    Lunar images from the Galileo spacecraft as Raw Experimenter Data Records (REDRs) are available for the first Earth flyby, which occurred in late 1990. This CD-ROM set will eventually include all of the Galileo cruise phase imaging (all images from the Solid-State Imager prior to Galileo's main mission at Jupiter), including those of Venus, the Earth, the Moon, and the asteroids Gaspra and Ida. The data for the Earth-2 flyby have recently arrived (Feb. 1995) and are now available.

    There are also Earth-based radar images of the Moon on the Pre-Magellan CD-ROM.

    More information on CD-ROMs available from the NSSDCA can be found in the NSSDCA CD-ROM Catalog.
    URL: http://nssdc.gsfc.nasa.gov/cd-rom/

  2. Where can I get Lunar Digital Image/Terrain/Elevation Models/Maps?

    NSSDCA has a Lunar Digital Image Model (data set SL-21D) available on magnetic tape. The model is a global sinusoidal projection of an airbrush map of the Moon with a resolution of about 900 m/pixel. More information on DIMs of the Moon and other planets and satellites is available on the Digital Image Models Page.
    URL: http://nssdc.gsfc.nasa.gov/planetary/dims.html

    Topography data (and gravity data) can be found at:

    http://pds-geophys.wustl.edu/pds/clementine/gravity_topo/

  3. Did the Apollo astronauts really land on the Moon?

    Of course they did! The Apollo Moon landings were among the most completely documented and observed events in history. Moon rocks have been examined by scientists from all over the world, not just the U.S. Video special effects were in their infancy in the late 60's so that faking a landing on the Moon would probably have been more difficult than actually going there, and it seems highly unlikely that the hundreds or even thousands of people who would have had to be involved in such a conspiracy would have kept it a secret for so long. Ultimately you'll have to decide for yourself if any evidence offered to show this was all a hoax is compelling enough to overturn the overwhelming evidence that it actually occurred, but make sure you check the facts carefully, you need to be a little skeptical of the skeptics, too. For more detailed information, see:

    http://www.badastronomy.com/bad/misc/apollohoax.html

    http://pirlwww.lpl.arizona.edu/~jscotti/NOT_faked/

    http://web.archive.org/web/20051023205705/www.rationalinquiry.org/essays/moon_lowman.html

    http://www.redzero.demon.co.uk/moonhoax/

    http://www.clavius.org/

    http://www.braeunig.us/space/hoax.htm


Mars

General

  1. Where is the "face" on Mars located?

    The so-called "face" on Mars is located in the Cydonia Mensae region at roughly 40.9 degrees North latitude and 9.45 degrees West longitude.

  2. How many pictures were taken of the "face"?

    As many as 18 images of the region were taken by the Viking 1 and 2 orbiters, but only seven have resolutions better than 250 m/pixel. The other 11 images have resolutions worse than 550 m/pixel and are virtually useless for studying the feature. Of the seven "good" images, the lighting and time at which two pairs of images were taken are so close as to reduce the number to five usable, distinct images. All five of these can be seen at the NSSDCA Photo Gallery in raw and processed forms as JPEGS. They are also available as TIFF files in the raw form only on the NSSDCA Photo Gallery FTP site for Mars images. Finally, they are available in PDS image format on the NSSDCA's FTP site for CD-ROMs.

  3. Which images have the "face" on them?

    The best images of the "face" can be found in the following Viking images/CD-ROMs (cf. Mission to Mars: Viking Orbiter Images of Mars CD-ROMs):

    The first two images in the list show the "face" clearly (resolutions of 47 and 43 m/pixel, respectively). The others are lower resolution (163, 226, and 233 m/pixel, respectively). Detailed image parameters are available for 35A72 and 70A13. All seven of these images have been made available in PDS format on the NSSDCA's FTP site for CD-ROMs.

  4. What other interesting features are visible on Mars?

    This list is not intended to be comprehensive, but for example frequently requested photos of the so-called "pyramids" (located near the "face") are in frames 35A70, 35A71, 35A73, 35A74 (all on disc VO-1010), 70A11, 70A12, and 70A14 (all on VO-1011). A feature known as the "water spout" is in the images 775A10 and 775A11 (both on disc VO-1029). A feature which resembles a permafrost melt is in images 182B03 and 182B05 (both on disc VO-1054). Finally, a feature called "Inca City covered over" is in image 225B69 on disc VO-1055.

  5. What is NASA's official opinion as to what the "face" on Mars is?

    NASA has no official opinion on what the so-called "face" on Mars is. Most planetary scientists agree that, although there is insufficient data to make a definitive analysis of the feature, it is highly unlikely to be anything other than a combination of a natural feature and unusual lighting conditions.

  6. How far is it between the Viking and Mars Pathfinder landing sites (or other features)?

    The answer to this question can be found on the Martian Mileage Guide. The distance in both miles and kilometers between the Viking and Mars Pathfinder sites and some other features is given.
    URL: http://nssdc.gsfc.nasa.gov/planetary/mars_mileage_guide.html

  7. Where can I get Martian Digital Image/Terrain/Elevation Models/Maps?

    Digital terrain models of Mars are available in the Mission to Mars CD-ROM set on Volume 7:Global Topography at resolutions of 1/4, 1/16 and 1/64 degree/pixel. This volume also contains mosaicked digital image models at 1/16 and 1/64 degree/pixel and digitized airbrushed maps of Mars at 1/4 and 1/16 degree/pixel. Higher resolution (1/256 and 1/64 degree/pixel) regional digital image models and 1/16 and 1/64 degree/pixel regional digitized airbrush maps are available on Volumes 1-6 of this set. Digital color mosaics are available on volumes 8-14 at 1/64 degree/pixel. More information on DIMs of Mars and other planets and satellites is available on the Digital Image Models Page.
    URL: http://nssdc.gsfc.nasa.gov/planetary/dims.html

Viking

  1. What do the file names for the images and directories on the Viking Orbiter CD-ROMs mean?

    Images on the Mission to Mars: Viking Orbiter Images of Mars CD-ROMs (volumes VO_10xx) are given a designation of the form FxxxZyy, where xxx is a three digit number indicating the orbit number, Z is a capital letter indicating the mission: A and S are Viking Orbiter 1, B is Viking Orbiter 2, C and D indicate images taken by Viking 1 and 2 respectively before orbit insertion, X and Y indicate Viking Orbiter 1 and 2 images, respectively, acquired in an orbit with more than 100 images. The last 2 digits, yy, give the sequential number of an image taken within a given orbit. For example, F443A10 is the 10th Viking 1 image taken on orbit 443; F004Y01 is the 100th Viking 2 image taken on orbit 4.

  2. Are there CD-ROMs available for any of the other Viking experiments?

    Yes, the Viking Orbiter 1 and 2 Infrared Thermal Mapper (IRTM) data are available on CD-ROM from the Planetary Data System.

  3. Are the Viking Lander images available on CD-ROM?

    No, not at this time. PDS is planning to put the images on CD-ROM for distribution sometime in the near future. However, Viking Lander images are available on-line through the PDS imaging node Viking Lander Image Browser. The Viking Lander images are also available from NSSDCA in photographic or digital format.

    More information on CD-ROMs available from the NSSDCA can be found in the NSSDCA CD-ROM Catalog.
    URL: http://nssdc.gsfc.nasa.gov/cd-rom/

  4. Why are the colors different on different Viking Lander images?

    The Viking Lander imagers had three visible filters and three near-infrared filters. The visible filters were blue, green, and red multilayer interference filters which had very irregular spectral response, including a response to infrared light. Therefore, producing a "true" color image required the scene to be imaged in all six filters and an integrated spectral solution developed. The saturation levels at each wavelength also had to be estimated. Finally, with three visible filters, the radiance at all wavelengths not covered by these filters had to be estimated based on the response at the filter wavelengths. An array of color chips was mounted on the spacecraft to mitigate some of these problems, but accurate color reconstruction of the array in the final image, though necessary, was not sufficient to guarantee true color. Since many of the images did not have all this information available, the colors can vary significantly from image to image based on the reconstruction techniques used. It is believed that the closest to "true" color images of Mars (i.e., what one would see standing on the surface) show a light orange sky (due to suspended dust in the atmosphere) and a yellowish cast on the surface (due to sunlight filtering through the dust).
    (Some Viking lander images can be seen in the NSSDCA Photo Gallery.)

Mars Observer

  1. What happened to the Mars Observer?

    An independent NASA review board concluded that the most likely cause of the loss of communication with the Mars Observer was a rupture in a line in the propulsion system during the start of fuel tank pressurization. The board cautioned that "There was no specific evidence about what actually transpired during the pressurization sequence".

    On August 21, 1993 the spacecraft transmitters were turned off during the final approach to Mars to protect the components against shock from the pressurization sequence. After the transmitter was turned off the tanks were supposed to be pressurized and then the transmitters turned back on and communications with Earth resumed, but no further signals were ever received on Earth. The hypothesis is that a small amount of nitrogen tetroxide may have leaked through the check valves during the 11 month voyage to Mars and condensed in the pressurization lines. During pressurization, the oxidant would have mixed with the monomethylhydrazine fuel, causing combustion and rupture of the fuel lines. The resultant high-pressure expulsion of gasses through the rupture would have started the spacecraft spinning uncontrollably and making communication with Earth impossible. The reason that this was considered to be the most likely scenario is that the pressure check valves were not designed for a mission in which tank pressurization took place after 11 months, but rather for a pressurization soon after launch. The decision to pressurize just before entering Mars orbit was made after the check valves were already built. It is therefore likely that some oxidant could have leaked past the valves over the 11 month period.

    Other scenarios that were considered likely were: 1) A failure of the pressure regulator, causing the oxidizer tank to burst, 2) A massive short in the electrical system, or 3) Damage to the fuel tank caused by an impact from one of the pyrotechnic devices fired to open valves in the pressurization lines.


Asteroids

  1. Are there any CD-ROMs with asteroid images on them?

    Yes. Volume 7 of the Galileo imaging set, which contains all of the Galileo images of Gaspra as Raw Experimenter Data Records (REDRs), has the data from the Gaspra flyby. Volume 16 of the same set has data from the Ida flyby. This CD-ROM set includes all of the Galileo cruise phase imaging (all images from the Solid-State Imager prior to Galileo's main mission at Jupiter), including those of Venus, the Earth, the Moon, the asteroids Gaspra and Ida, and the images taken by the SSI instrument during the Comet Shoemaker-Levy 9 impact on Jupiter.

    More information on CD-ROMs available from the NSSDCA can be found in the NSSDCA CD-ROM Catalog.
    URL: http://nssdc.gsfc.nasa.gov/cd-rom/


Jupiter

General

  1. Where can I find on-line images of Jupiter taken during and after the impacts of comet P/Shoemaker-Levy 9?

    A large number of images of this type are available on NSSDCA's Comet Impact page. This page also provides links to other observatories and collections of images.
    URL: http://nssdc.gsfc.nasa.gov/sl9/comet_images.html

  2. Are data for the fields and particles experiments on Pioneer 10/11 and/or Voyager 1/2 and/or Ulysses available on CD-ROM for the Jupiter encounter?

    No. Some of these data are still being processed by the Planetary Data System's Planetary Plasma Interactions (PPI) node but are expected in 1995 prior to Galileo's arrival at Jupiter.

    More information on CD-ROMs available from the NSSDCA can be found in the NSSDCA CD-ROM Catalog.
    URL: http://nssdc.gsfc.nasa.gov/cd-rom/

  3. Are Digital Image/Terrain/Elevation Models/Maps available for the Jovian satellites?

    Low-resolution airbrush global digital image models in sinusoidal equal area projection of the Jovian satellites Io, Europa, Ganymede, and Callisto are available on magnetic tape and as photoproducts from NSSDCA (data sets SL-21E and SL-21F). More information on these DIMs and DIMs of other planets and satellites is available on the Digital Image Models Page.
    URL: http://nssdc.gsfc.nasa.gov/planetary/dims.html

Pioneer 10 and 11

  1. Are any of the imaging data from Pioneer 10 or 11 available on CD-ROM from the Jupiter encounters?

    No. There is not currently any expected delivery on Pioneer 10 or 11 imaging data on CD-ROM.

    More information on CD-ROMs available from the NSSDCA can be found in the NSSDCA CD-ROM Catalog.
    URL: http://nssdc.gsfc.nasa.gov/cd-rom/

Voyager 1 and 2

  1. Why are some images missing from the Jupiter flyby on the Voyager imaging CD-ROMs?

    When the Voyager imaging CD-ROMs were first being produced, it was recognized that the volume of images from the Jupiter encounter, if included in total, would take up many more volumes than desired. This would have included a number of poor images (with signal dropouts, etc.). Rather than delay the release of the better images, it was decided to place only the "best" of the images on the discs, resulting in Volumes 6-8 of the Voyager imaging CD-ROM set. Once all of the images from the Voyager flybys had been placed on CD-ROM, the decision was made to go back and put all of the Voyager images from the Jupiter encounter on CD-ROM. These begin with Volume 13 and will last until approximately Volume 25 of the series. These images will supercede those on the earlier volumes. The latest volume to arrive at NSSDCA was Volume 24, which covers through image 20617.37. Additional volumes are arriving approximately every other month in odd numbered months.


Saturn

General

  1. Are data for the fields and particles experiments on Pioneer 11 and/or Voyager 1/2 available on CD-ROM for the Saturn encounter?

    No. Some of these data are still being processed by the Planetary Data System's Planetary Plasma Interactions (PPI) node.

    More information on CD-ROMs available from the NSSDCA can be found in the NSSDCA CD-ROM Catalog.
    URL: http://nssdc.gsfc.nasa.gov/cd-rom/

  2. Are Digital Image/Terrain/Elevation Models/Maps available for the Saturnian satellites?

    Low-resolution airbrush global digital image models in sinusoidal projection of the Saturninan satellites Mimas, Enceladus, Tethys, Dione, Iapetus, and Rhea are available on magnetic tape and as photoproducts from NSSDCA (data sets SL-21G and SL-21H). More information on these DIMs and DIMs of other planets and satellites is available on the Digital Image Models Page.
    URL: http://nssdc.gsfc.nasa.gov/planetary/dims.html

Pioneer 11

  1. Are any of the imaging data from Pioneer 11 available on CD-ROM from the Saturn encounters?

    No. There is not currently any expected delivery on Pioneer 11 imaging data on CD-ROM.

    More information on CD-ROMs available from the NSSDCA can be found in the NSSDCA CD-ROM Catalog.
    URL: http://nssdc.gsfc.nasa.gov/cd-rom/

Voyager 1 and 2

  1. Why are some images missing from the Saturn flyby on the Voyager imaging CD-ROMs?

    When the Voyager imaging CD-ROMs were first being produced, it was recognized that the volume of images from the Saturn encounter, if included in total, would take up many more volumes than desired. This would have included a number of poor images (with signal dropouts, etc.). Rather than delay the release of the better images, it was decided to place only the "best" of the images on the discs, resulting in Volumes 4-5 of the Voyager imaging CD-ROM set. Recently it has been decided to go back and put all of the Voyager images from the Saturn encounters on CD-ROM. These will begin with Volume 26 and will last until approximately Volume 35 of the series. These images will supercede those on the earlier volumes. These volumes are expected to begin arriving at NSSDCA no earlier than September 1995.


Uranus

  1. Does NSSDCA have Voyager 2 data at Uranus on CD-ROM?

    Yes. There are three volumes (Volumes 1-3) of the Voyager imaging CD-ROM set which contain images of Uranus and its satellites. In addition, a single volume (Volume 2) of the Outer Planets Fields and Particles CD-ROMs contains data from all of the fields and particles instruments. Not represented on CD-ROM at this time are data from the infrared spectrometer (IRIS), ultraviolet spectrometer (UVS), and radio science experiments.

    More information on CD-ROMs available from the NSSDCA can be found in the NSSDCA CD-ROM Catalog.
    URL: http://nssdc.gsfc.nasa.gov/cd-rom/

  2. Are Digital Image/Terrain/Elevation Models/Maps available for the Uranian satellites?

    Low-resolution airbrush global digital image models in sinusoidal projection of the Uranian satellites Miranda, Ariel, Umbriel, Titania, and Oberon are available on magnetic tape and as photoproducts from NSSDCA (data sets SL-21I and SL-21J). In addition, mosaicked digital image models of these satellites are available in the same formats (data sets SL-21K and SL-21L). More information on these DIMs and DIMs of other planets and satellites is available on the Digital Image Models Page.
    URL: http://nssdc.gsfc.nasa.gov/planetary/dims.html


Neptune

  1. Does NSSDCA have Voyager 2 data at Neptune on CD-ROM?

    Yes. There are four volumes (Volumes 9-12) of the Voyager imaging CD-ROM set which contain images of Neptune and its satellites. In addition, a single volume (Volume 1) of the Outer Planets Fields and Particles CD-ROMs contains data from all of the fields and particles instruments. Not represented on CD-ROM at this time are data from the infrared spectrometer (IRIS), ultraviolet spectrometer (UVS), and radio science experiments.

    More information on CD-ROMs available from the NSSDCA can be found in the NSSDCA CD-ROM Catalog.
    URL: http://nssdc.gsfc.nasa.gov/cd-rom/

  2. Are Digital Image/Terrain/Elevation Models/Maps available for the Neptunian satellites?

    No. The Astrogeology Branch of the United States Geological Survey in Flagstaff, Arizona, which produces such things, has not indicated that such a product is forthcoming. They should be contacted for further information. Information on DIMs of other planets and satellites is available on the Digital Image Models Page.
    URL: http://nssdc.gsfc.nasa.gov/planetary/dims.html


Pluto

  1. Is Pluto a planet?

    No, Pluto is no longer considered a planet like the other eight planets in our solar system. The body that decides the classification of objects in the solar system, the International Astronomical Union (IAU), has voted on a new scientific definition of "planet" which states that a planet is a celestial body that:

    (a) is in orbit around the Sun

    (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and

    (c) has cleared the neighbourhood around its orbit. Pluto does not meet the third criterion, it has not cleared the region of its orbit of other "competing" bodies, so it has been reclassified, along with the asteroid Ceres and the Kuiper Belt Object 2003 UB313, as a "dwarf planet" (which even though it has the word "planet" within it is not considered to be a type of planet).

    For more details, see the IAU resolution.

  2. Are there any planned missions to Pluto?

    Yes. The NASA New Horizons mission is scheduled to launch in January 2006 and reach Pluto in 2015.

  3. Is there a "Planet X", a planet beyond the orbit of Pluto?

    No, not officially. It turns out that there's a large belt of comets orbiting beyond Pluto, called the Kuiper Belt. One object has already been discovered in this belt that is reliably estimated to be larger than Pluto, but it has not been officially designated a planet. It seems likely many more bodies larger than Pluto will be discovered. It's possible that the object Chiron, currently inside the orbit of Saturn, was one of these objects which escaped. More information on Chiron and the Kuiper Belt is available.


Comets

  1. Where can I find on-line images of Comet P/Shoemaker-Levy 9?

    Images of the comet before impact with Jupiter, as well as images of the collisions and their effects on Jupiter are available on NSSDCA's Comet Impact page. This page also provides links to other observatories and collections of images.
    URL: http://nssdc.gsfc.nasa.gov/planetary/sl9/comet_images.html

  2. Are there CD-ROMs with comet data on them?

    Yes. The International Halley Watch (IHW) CD-ROMs have data and images of comets P/Halley, P/Crommelin, and P/Giacobini-Zinner in PDS and FITS formats. There are also plans for CD-ROMs in FITS format with data for comets P/Shoemaker-Levy 9 and P/Grigg-Skjellerup.

    In addition to this, images taken by the Galileo Solid-State Imager (SSI) of Comet Shoemaker-Levy 9's impact on Jupiter are available on Volume 16 of the Galileo imaging set, which also contains all available images of the asteroid Ida, as Raw Experimenter Data Records (REDRs).

    More information on CD-ROMs available from the NSSDCA can be found in the NSSDCA CD-ROM Catalog.
    URL: http://nssdc.gsfc.nasa.gov/cd-rom/


Questions and comments about this page should be addressed to:
Dr. David R. Williams, david.r.williams@gsfc.nasa.gov, (301) 286-1258
NSSDCA, Mail Code 690.1, NASA Goddard Space Flight Center, Greenbelt, MD 20771
or
Dr. Edwin V. Bell, II, ed.bell@gsfc.nasa.gov, (301) 286-1187
NSSDCA, Mail Code 690.1, NASA Goddard Space Flight Center, Greenbelt, MD 20771

NASA Official: Dr. Ed Grayzeck Last Updated: 07 October 2008, DRW