Help Page for the Galileo SSI Image Catalog 1.0

The Galileo Solid State Imager (SSI) Catalog makes it possible to select images from the PDS CDROMs based on a broad variety of constraints. For example, you can quickly identify all the Jovian ring images for which the filter was CLEAR and the phase angle was greater than 90 degrees. You accomplish this by entering the appropriate values into the fields you see on the form and then clicking on the Submit Query button at the bottom of the page. After a short wait, you will see a listing of all the images that match the constraints you have entered.

Change History

1.0 (11 March 2002) Original catalog form on line.

INDEX

Query Options

Glossary


INSTRUCTIONS

The Galileo Solid State Imager (SSI) Image Catalog makes it possible to select images from the PDS CDROMs based on a broad variety of constraints. You can accomplish this by entering values into the fields you see on the form and then clicking on the Submit Query button at the bottom of the page. After a short wait, you will see a listing of all the Galileo images on the CDROMs that match the constraints entered.

The numerous fields on this form permit you to enter many different kinds of constraints. In most cases, entering values in different fields results in an "and" operation. For example, if you select Filter=CLEAR and Target name=JRINGS, you will see all the clear-filter images targeted at the Jovian ring. However, selecting values within the same group of parameters results in an "or" operation. For example, if you select Targets = ADRASTEA and then select Targets = METIS in the next column, you will find all the images targeted at either Adrastea or Metis. If you leave a field blank, that particular parameter is unconstrained. Since there are so many fields on the form, it is very common for most of them to be blank.

Use the Listing type box near the bottom of the page to choose among three possible ways to display the results of a query. Match Count simply counts the number of matching images in the database but does not return a list. A Summary listing returns a table of the matching images in addition to the match count. This is the default. A summary listing can return up to 1000 images at a time. A Detailed listing returns a detailed summary of every parameter for each matching image, in addition to the match count and summary listing. A detailed listing can return up to 100 images at a time. If you exceed the image limit for either a summary or detailed listing, you can see the remaining images by entering a number of images to skip over into the Skip box.

Once you made your selections, click on the Search Catalog button at the bottom of the page to submit your query. If at any time you wish to erase all of your entries in the form and start over, click on the Reset Form button.

Ordering Data

A detailed listing returns a list of file names.

The Galileo image CDROM containing a particular image can be determined by examining the REDR file name field of a detailed listing. The full directory path is shown, beginning with the CDROM volume ID of the form GO_00xx.

Alternatively, you may simply email a request to Neil Heather. We can also fill requests for limited numbers of images by electronic transfer.

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QUERY OPTIONS

Listing type

Three listing types are supported. A Match Count simply counts the number of matching images in the database but does not return a list. A Summary listing returns a table of the matching images in addition to the match count. A Detailed listing returns a detailed summary of every parameter for each matching image, in addition to the match count and summary listing.

Match Count

When the Match Count listing type is selected, you only see the number of unique images in the database that match the given constraints.

Query listings always begin with a summary of the SQL query and the options selected, followed by the number of matches. SQL is the language used by the database; you do not need to understand it but, if a query fails, please report this text to the Rings Node to help us to diagnose the problem.

Summary listing

When the Summary listing type is selected, you will see the typical Match Count listing followed by a table of the matching images. This is the most common type of query and serves as the default. Only the most often used parameters of each image are listed; if you need more information, repeat the same query while requesting a Detailed listing. The parameters included in a Summary listing are the Query record, Spacecraft clock count, nominal target name, observation ID (which includes the orbit number), exposure duration in msec, filter name, and ring information flag.

Note that a Summary listing query is limited to 1000 matches. If more matches are found, only the first 1000 will be shown. The Match Count section will list both the number of matches found and the (possibly smaller) number listed in the table. Repeat the query with a number entered into the Skip the first _____ matches field to see the additional images.

Detailed listing

When the Detailed listing type is selected, you will see the typical Match Count listing and Summary listing first. Following is a list of every database parameter for each matching image. In addition, the Summary listing section has active links to each section of the Detailed listing; simply click on the record number in the summary to jump to the detailed information.

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Skip the first _____ matches

The number of matches returned from a query is limited to 1000 for a summary listing and 100 for a detailed listing You can view additional images via the Skip the first _____ matches option. Just repeat the query with a number entered into this field, and that number of images will be skipped. For example, a value of 100 will mean that matching images 101-200 will be shown on a detailed listing (or 101-1100 on a summary listing).

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GLOSSARY

Central body distance

Central body distance is the distance in km between Galileo and the center of Jupiter.

On the query form, you can enter minimum and a maximum values, and only those images with central body distances between the two values (inclusive) will be returned.

The value of this parameter appears in a detailed listing but not a summary listing.

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Center ring radius

Center ring radius is the ring radius at the center of the image in km. It is only applicable to ring images. In this database, the value is always 180,000 km for ring images and undefined otherwise.

This parameter cannot be constrained on the query form. Its value is only shown on a detailed listing.

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Compression ratio

Compression ratio describes the mean compression ratio applied to the data on board the spacecraft. For Galileo, this keyword is valid only for Integer Cosine Transform (ICT) or Huffman compression.

This parameter cannot be constrained on the query form. Its value does not appear in a summary listing. In a detailed listing, the mean, minimum and maximum compression ratios are all listed.

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Compression type

Compression type indicates the type of compression/encoding applied to the image when on the spacecraft. Possible values are BARC_RATE_CONTROL, HUFFMAN, INTEGER_COSINE_TRANSFORM, and NONE.

This parameter cannot be constrained on the query form. Its value is only shown on a detailed listing.

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Cone angle

The Cone angle is the angle in degrees between the primary spacecraft axis and the pointing direction of the instrument.

This parameter cannot be constrained on the query form. Its value is only shown on a detailed listing.

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Data set ID

Data set ID is the name that PDS has attached to the data set. Possible values are GO-J/JSA-SSI-2-REDR-V1.0 and GO-J/JSA-SSI-4-REDR-V1.0.

This parameter cannot be constrained on the query form. Its value is only shown on a detailed listing.

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Declination

See Right ascension and declination.

Emission angle

Emission angle is the angle between the surface normal vector at the intercept point and a vector from the intercept point to the spacecraft. It is calculated at the center of the image. It varies from 0 degrees when the spacecraft is viewing the sub-spacecraft point (nadir viewing) to 90 degrees when the intercept is tangent to the surface of the target body. Thus, higher values of emission_angle indicate more oblique viewing of the target. Note that values in the range of 90 to 180 degrees are possible for ring data and indicate that the unlit side of the ring is in view.

On the query form, you can enter a range of values and only images with emission angles within the specified range will be returned. The value of this parameter appears in both the summary and detailed listings.

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Exposure duration

Exposure duration is the time interval between the opening and closing of the camera shutter, in milliseconds.

On the query form, you can enter values for a minimum and a maximum exposure duration, and only those images with exposure times between the two values (inclusive) are returned. If the first field is left blank, a minimum of zero is assumed; if the second is left blank, the maximum exposure time is effectively infinite.

On a summary listing, the exposure duration is listed under the Texp heading. The value is also included on the detailed listing.

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Filter name

The Galileo Solid State Imager has several color filters, named CLEAR, VIOLET, GREEN, RED, IR-7270, IR-7560, IR-8890, and IR-9680.

On the query form, you can select up to three different color filters, and only images taken through one of these filters are returned, as if an "or" operation were being performed. The filter name appears in both the summary and detailed listings. In the detailed listing the filter number (0-7) is also included.

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Frame duration

Frame duration records the scan rate of the camera readout in seconds. Valid values for Galileo are 2.333, 8.667, 30.333, and 60.667.

This parameter cannot be constrained on the query form. Its value is only shown on a detailed listing.

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Gain mode ID

Gain mode ID records the gain mode of the camera for the given image. Possible valures are 400K, 100K, 40K, and 10K.

This parameter cannot be constrained on the query form. Its value is only shown on a detailed listing.

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Horizontal pixel scale

Horizontal pixel scale indicates the spatial scale (m/pixel) of an image along the image's horizontal (sample) axis. See also vertical pixel scale.

On the query form, you can enter a range of values and only images with pixel scales within the specified range will be returned. The value of this parameter appears only in detailed listings.

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Image ID

The Image ID takes the form of XXYnnnn. Here nnnn is the picture count, which is generated in the sequence generation process and which is incremented separately for each target body in each orbit.

On the query form, four different types of matches are permitted.

This parameter appears in a detailed listing but not a summary listing.

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Incidence angle

The incidence angle indicates the angle between the local vertical at the intercept point on a target and a vector from the intercept point to the sun. It is calculated at the center of the image. A value of 0 coincides with the sub-solar point; a value of 90 degrees indicates a point at the terminator (i.e., on the border between the shadowed and lit portions of the target body). Thus, higher values of incidence angle indicate the existence of a greater number of surface shadows.

On the query form, you can enter a range of values and only images with incidence angles within the specified range will be returned. The value of this parameter appears in both the summary and detailed listings.

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Intercept point latitude and longitude

The intercept point latitude and longitude indicate where an intercept point intersects the target body. It is calculated at the center of the image. Values are given in degrees.

On the query form, you can specify a minimum and maximum value for both coordinates, and only images in which the center pixel falls within the specified range are returned. Values are listed in the detailed listing but not the summary listing.

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Local hour angle

Local hour angle indicates the instantaneous apparent Sun position at the sub-spacecraft point. It is the angle between two vectors projected into the target body's equatorial plane: (a) a vector from the Sun to the target body and (2) a vector from the target body's center to Galileo. This angle is measured in a counterclockwise direction when viewed from the body's north pole, in degrees.

On the query form, you can enter a range of values and only images with local hour angles within the specified range will be returned. The value of this parameter appears in both the detailed listing but not the summary listing.

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North azimuth

The north azimuth angle indicates the angle between a line from the image center to the north pole and a reference line in the image plane, in degrees. The reference line is a horizontal line from the image center. This angle increases in a clockwise direction.

This parameter cannot be constrained on the query form. Its value is only shown on a detailed listing.

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Observation ID

The observation ID is the Galileo activity identifier of each image. It is in the form NNTIOOOOOOMM#SSSXXXX, where NN is the orbit number; T is the scan platform target body initial (if applicable); I is the instrument; OOOOOO is the orbit planning guide objective mnemonic; MM is the sequential OAPEL number for each value of NNTIOOOOOO; # is the multiple observation flag symbol (- or *); SSS is the PA set number; XXXX is the MIPL Processing Code.

This parameter cannot be constrained on the query form. Its value appears in both the summary and detailed listings.

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Observation time

The observation time gives the time UTC at which the given image was acquired by Galileo.

The Image time can be constrained as a part of a query. The user can specify the minimum, maximum or both, and only images obtained within that range of times are returned. The time format is extremely general; click here for the gory details.

This parameter does not appear in the summary listing. In the detailed list it is given in PDS format, of the form "yyyy-mm-ddThh:mm:ss.sss".

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Obstruction ID

The obstruction ID identifies if the boom was obscuring the view of the camera during the exposure. Valid values are POSSIBLE, NOT_POSSIBLE, and PRESENCE_VERIFIED.

This parameter cannot be constrained on the query form. Its value is only shown on a detailed listing.

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Orbit number

The orbit number identifies the number of the orbital revolution of the spacecraft around Jupiter.

On the query form, you can enter a pair of values and only images with orbit numbers between those two values (inclusive) will be returned. The value for this parameter appears in both the summary and detailed listings.

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Phase angle

The phase angle is the angle between the direction to the Sun and the direction to Galileo, as viewed at the target. It is measured in degrees.

On the query form, you can enter a pair of values and only images with phase angles between those two values (inclusive) will be returned. The value for this parameter appears in both the summary and detailed listings.

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Processing history

The processing history field summarizes the VICAR image processing steps that have been applied to the image.

This parameter cannot be constrained on the query form. Its value is only shown on a detailed listing.

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Query record

The Query record is a temporary identifier for each of the matching images found by the most recent query. Values range from 001 to the total number images found.

Note that the query record number counts all matching records, regardless of the particular query options selected. For example, if you have chosen to skip the first 100 matches, then query record values on the listing will begin with 101.

Query record values appear as the first column in a summary listing, under the heading #. When a detailed listing is requested, each # in the summary table serves as a hypertext link to the detailed information for the same image.

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REDR image file name

The REDR image file name contains the PDS volume ID followed by the full directory path to the raw data file, in Unix format. "REDR" stands for "raw experiment data record."

This parameter cannot be constrained on the query form. Its value is only shown on a detailed listing.

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Right ascension and declination

The right ascension and declination describe the line of sight of the image center in J2000 celestial coordinates, in degrees.

These parameters, combined with the twist angle, define the C-matrix, which transforms a 3-vector in celestial coordinates into a frame fixed in the image plane. Celestial coordinates refer to a frame in which the x-axis points toward the First Point of Aries and the z-axis points to the celestial pole. Image plane coordinates are defined such that the x-axis (sample direction) points right, the y-axis (line direction) points down, and the z-axis points along the camera's optic axis.

The C-matrix is defined as follows:

Here R refers to right ascension, D to declination, and T to twist angle.

These parameters cannot be constrained on the query form. Its value is only shown on a detailed listing.

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Ring observation ID

The Ring observation ID is used by the Rings Node as a unique identifier for data in the catalog. For Galileo SSI images it has the form "J/IMG/GLL/SSI/nnnnnnn.nn" where nnnnnnn.nn is the spacecraft clock start count.

This parameter cannot be constrained on the query form. Its value is only shown on a detailed listing.

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Slant distance

The slant distance measures the distance in km from Galileo to a point on the target body at the center of the image.

On the query form, you can enter minimum and/or maximum values and only images with slant distances within the specified range are returned. This parameter appears in the detailed listing but not the summary listing.

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Smear azimuth

The smear azimuth indicates the direction in which an image was smeared. The angle is measured clockwise from a horizontal reference line, in degrees.

This parameter cannot be constrained on the query form. Its value is only shown on a detailed listing.

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Smear magnitude

The smear magnitude indicates how far an image was smeared during an exposure.

This parameter cannot be constrained on the query form. Its value is only shown on a detailed listing.

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Solar distance

The solar distance indicates the distance from the center of the target body body to the center of the Sun, in km.

This parameter cannot be constrained on the query form. Its value is only shown on a detailed listing.

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Spacecraft clock start count

The spacecraft clock start count indicates the time on the spacecraft clock at the time the camera shutter opened. It format is "(8 digits).(2 digits)".

On the query form, you can enter a pair of values and only images with counts between those two values (inclusive) will be returned. The value for this parameter appears in both the summary and detailed listings.

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Sub-solar azimuth

The sub-solar azimuth is the angle from a horizontal reference line in the image and the subsolar point, i.e. the point on the target body where a vector from the Sun's center to the target body's center intersects the surface. This indicates the orientation of shadows in the image. It is measured in a clockwise direction, in degrees.

This parameter cannot be constrained on the query form. Its value is only shown on a detailed listing.

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Sub-solar latitude and longitude

The sub-solar latitude and longitude describe the location on the target body where a vector from the Sun's center to the target body's center intersects the surface. The latitude is planetocentric and longitude increases toward the west. Angles are measured in degrees.

These parameters cannot be constrained on the query form. Its value is only shown on a detailed listing.

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Sub-spacecraft latitude and longitude

The sub-spacecraft latitude and longitude describe the location on the target body where a vector from Galileo to the target body's center intersects the surface. The latitude is planetocentric and longitude increases toward the west. Angles are measured in degrees.

These parameters cannot be constrained on the query form. Its value is only shown on a detailed listing.

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Sub-spacecraft line and sample

Sub-spacecraft line and sample specify the coordinates in the image where the sub-spacecraft point falls. The sub-spacecraft point is the location on the target body where a vector from Galileo to the target body's center intersects the surface.

This parameter cannot be constrained on the query form. Its value is only shown on a detailed listing.

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Sub-spacecraft longitude

See Sub-spacecraft latitude and longitude.

Sub-spacecraft sample

See Sub-spacecraft line and sample.

Target center distance

Target center distance indicates the distance in km between Galileo and the center of the target body.

On the query form, you can enter minimum and/or maximum values and only images with target center distances within the specified range are returned. This parameter appears in the detailed listing but not the summary listing.

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Target name

The Target name parameter indicates the nominal target of each image. Note that an image can contain multiple objects but each image is cataloged with only a single nominal target. As a result, this parameter is not 100% reliable. For example, seekers of Jovian ring images should consider images targeted at ADRASTEA and METIS as well as those targeted at J_RINGS.

Possible targets are JUPITER, J_RINGS, METIS, ADRASTEA, AMALTHEA, THEBE, IO, EUROPA, GANYMEDE, CALLISTO, BLACK_SKY, NON_SCIENCE. Up to three different targets can be selected in any query; they are combined in the query via an "or" operation. The target is included in both summary and detailed listings.

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Time from Jupiter approach

The time from Jupiter approach is the time relative to the closest approach to Jupiter on the given orbit. The format is +/- ddThh:mm:ss, consisting of days, hours, minutes and seconds. Negative values refer to times before closest approach; positive values refer to times after.

This parameter cannot be constrained on the query form. Its value is only shown on a detailed listing.

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Time from target approach

The time from target approach is the time relative to the closest approach to the target body on the given orbit. The format is +/- ddThh:mm:ss, consisting of days, hours, minutes and seconds. Negative values refer to times before closest approach; positive values refer to times after.

This parameter cannot be constrained on the query form. Its value is only shown on a detailed listing.

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Twist angle

The twist angle indicates the image's angle of rotation about an optical axis relative to celestial coordinates. The right ascension, declination, and twist angle parameters together define the pointing and orientation of an image; see right ascension for full details.

For Galileo images, (270 degrees - twist angle) gives the clock angle of celestial north in the image. This is the angle of celestial north measured clockwise from the upward (decreasing line) direction in the image.

This parameter cannot be constrained on the query form. Its value is only shown on a detailed listing.

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Vertical pixel scale

Vertical pixel scale indicates the spatial scale (m/pixel) of an image along the image's vertical (line) axis. See also horizontal pixel scale.

On the query form, you can enter a range of values and only images with pixel scales within the specified range will be returned. The value of this parameter appears only in detailed listings.

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Last update 11 March 2002

Mark Showalter