Context Camera (CTX) Stamp Layer

From JMARS Wiki

The CTX Stamp Layer will display stamps for all of the images taken by the Context Camera (CTX) aboard the Mars Reconnaissance Orbiter. While the query interface is similar to the THEMIS Stamp Layer, there are some differences which allow users to search for images by the many parameters associated with CTX images. For more information on using the CTX Stamp Layer, click on the title above.

[edit] Open the CTX Stamp Layer

Open the Stamp Layer: Chose "Add New Layer" -> "Stamps" -> "CTX Stamps".

Search Parameter Categories: The search parameters are divided into categories since there are so many of them. Clicking on the down arrow on the right side of the category name will reveal all the search parameters in that category. The categories are:

• Basic Parameters
• Advanced Parameters

NOTE: A search can be done with parameters from multiple categories.

Enter Search Parameters: It is not necessary to enter values for each parameter, but the more specific your search the faster it will be. The allowable values for each field are given in the quick reference table below followed by more detailed descriptions of each search parameter.

Perform Image Search: Clicking OK will make the Stamp Layer perform the search and display the results. Depending on how specific the search parameters are, it may take the Stamp Layer a few minutes to find and create stamps for all of the images. Once the stamps are displayed in the Viewing Window, users can right-click on an outline to either render the image (display the image data in JMARS) or view the image in a web browser.

CTX Search Parameter Glossary

Filter Type

Acceptable Values

Basic Parameters
Image ID(s)	Any Image ID Numbers
Min/Max Longitude	0 - 360 - East Longitude = Positive, West Longitude = Negative Blank - All Longitudes
Min/Max Latitude	90 - -90 - North Latitude = Positive, South Latitude = Negative Blank - All Latitudes
Min/Max Orbit	Any Orbit Range Blank - All Orbits

Advanced Parameters
Mission Phase	POST-MOI - Post Mars Orbit Insertion PSP - Primary Science Phase Transition - Aerobraking Phase Blank - All Mission Phases
Spatial Summing
Scaled Pixel Width	1.0 - 7500.0 Blank - Any Scaled Pixel Width
Lines	xxx Blank - Any Lines
Line Samples	xxx Blank - Any Line Samples
Min/Max Solar Longitude	0 - 360 - 0=Northern Vernal Equinox Blank - All Solar Longitudes
Local Time (24hr)	00:00-24:00 - Given as HH:MM Blank - All Times
Min/Max Solar Incidence Angle	0 - 180 - 0=Sun Directly Overhead, 90=Sun on the Horizon Blank - All Incidence Angles
Min/Max Emission Angle	0 - 180 - 0=CTX Directly Overhead, 90=CTX on the Horizon Blank - All Emission Angles
Phase Angle	0 - 180 - 0=CTX and Sun In-Line, 90=CTX and Sun at 90deg Angle Blank - All Phase Angles
Slant Distance	0 - 5000 - Distance from sub-MRO point to image center (in meters) Blank - All Slant Distances
Rationale Description	Any Text Blank - Any Rationale Descriptions

Search Field Descriptions

Image ID

A unique identifier for each image commanded.

Longitude

This is the approximate longitude on the planet Mars of the image center. All values are based on the IAU 2000 aerocentric model of Mars with east positive longitude. (gives in degrees of East Longitude)

Latitude

This is the approximate latitude on the planet Mars of the image center. All values are based on the IAU 2000 aerocentric model of Mars with east positive longitude.

Orbit

Spacecraft orbit during which this image was observed. By definition, orbits begin at the ascending equator crossing of Global Surveyor's polar orbit.

Mission Phase

The MRO/CTX mission has been divided into the following phases:

Post-MOI Post Mars Orbit Insertion

PSP Primary Science Phase

Transition Aero-Breaking Period Prior to Final Orbit

Spatial Summing

Spatial average of NxN pixels of data before downlink; summing=1 implies that no spatial averaging has been applied.

Scaled Pixel Width

This is the image resolution in meters per pixel at the center of the image. For most narrow angle images, this value will be approximately the same over the entire picture. For wide angle images, the pixel scale will vary over the image.

Lines

Line Samples

Solar Longitude

This is the position of Mars relative to the Sun measured in degrees from the vernal equinox (start of northern Spring). This number is used as a measure of Martian seasons. (Also known as heliocentric longitude and abbreviated Ls.)

a) Northern Spring/Southern Autumn start at 0°

b) Northern Summer/Southern Winter start at 90°

c) Northern Autumn/Southern Spring start at 180°

d) Northern Winter/Southern Summer begin at 270°

Local Time'

This is the local time on Mars at the center of the image relative to a division of the martian day into 24 equal parts. A martian day is slightly longer than 24 hours and 37 minutes long.

Incidence Angle

Derived for the center of the image, this is the angle between the Sun and a "normal" drawn perpendicular to the planet's surface at the time the image was acquired. A higher incidence angle means that a person standing on the ground would see the sun lower toward the horizon.

Emission Angle

Measured from the center of the image, this is the angle between the CTX and a "normal" drawn perpendicular to the planet's surface.

Phase Angle

This is the angle between the sun, the surface, and the CTX at the time the picture was obtained.

Slant Distance

This number is similar to the spacecraft altitude, but also takes into account the emission angle. If the emission angle is 0 then this number is the same as the spacecraft altitude. If the emission angle is much greater than 0, then the "slant distance" to the surface at the center of the image is also greater than the spacecraft altitude.

Rationale Description

A short description of why the image was targeted.

[edit] Stamp Layer Functions

The CTX Stamp Layer's functions are identical to the functions of the Thermal Emission Image System (THEMIS) Stamp Layer and are explained in detail on its wiki page.