The Context Camera (CTX) is a camera on board the Mars Reconnaissance Orbiter (MRO) acquiring grayscale images at 6 meters per pixel scale over a swath 30 kilometers wide. CTX provides context images for the MRO HiRISE and CRISM observations, is used to monitor changes occurring on the planet, and acquires stereo pairs of selected, critical science targets.

Data description

The following CTX products are available on MarsSI:

• EDR image: Raw image in a standard format called the Experiment Data Record
• RDR image: Converted raw image into reflectance (irradiance/solar flux or I/F) called Radiometric Data Record
• MRDR image: Projected image from RDR image

The CTX files have names like P16_007430_1783_XN_01S083W.

Processing CTX data

The pipelines used for the data calibration and projection are those proposed by ISIS3 (https://isis.astrogeology.usgs.gov/index.html).

From the “Maps” tab, zoom-in on your region of interest, you can display the THEMIS mosaic for more precision, and then display the CTX layer. You get all CTX stamps that appear in green. The stamps are regularly updated to take into account new data. You can use the “Select” button to choose the stamp you desire. You can choose several stamps by clicking several stamps, or by dragging your mouse to select adjacent stamps. You can also use the “Search” button for more options.

To add your desired stamps to your cart click on “Add” in the “Cart” window, and go to the “Workspace” tab. Your CTX image appears in the window “Data to process”. If not, you may already have processed it yourself, or someone else may have processed it, then it may already be in the “Data processed” window. If the image has not been processed, you will have to go through several steps:

1. Download the CTX EDR image (rawdata) to the MarsSI server by clicking on the EDR image and the “Process” button in the “Data to process” window. This will take a few minutes.
2. When the first step is done, you can create a calibrated RDR image: click on the proposed RDR image in the “Data to process” window and on the “Process” button. This will take another few minutes, depending on the length of the CTX observation.
3. Project the CTX image by processing the proposed MRDR image in the “Data to process” window. This will take more time than the previous processes, another few minutes.

When these different steps are done, the MRDR image is waiting for you in the “Data processed” window and you can copy it to your FTP partition.

References

• CTX instrument description website: http://www.msss.com/all_projects/mro-ctx.php
• CTX instrument description paper: Malin et al., (2007), Context Camera Investigation on board the Mars Reconnaissance Orbiter, Journal of Geophysical Research, 112, E05S04, doi: 10.1029/2006JE002808.