Mariner 9

Spacecraft Description

Mariner 9 was the first Mars orbiter, arriving in mid-November 1971. The spacecraft operated in a 12h, ~1,600 x ~16,000 km, 65° inclination orbit.

Camera information

The spacecraft imaging system consisted of a 52 mm focal length wide-angle lens and 500 mm narrow-angle lens. A selenium sulfide vidicon (analog slow-scan TV) sensor was connected to each lens. Ghosting is an issue with Mariner 9 imagery, as image readout did not completely remove residual charge from bright areas of an image. As a result, faint residuals from an image couple appear in as many as three subsequent photos taken with that sensor. Each image was 832 x 700 px in size, returned at 8-bit resolution. Raw images need to be rescaled to 1033 x 700 px, since the imaging system used non-square (6.6 x 8.2 milliradian) pixels.

The narrow-angle camera system used a single filter that covered the entire spectral range of the vidicon sensor. The wide-angle camera system was equipped with an 8-filter wheel. Four filters (1, 3, 5, and 7) were broadband filters covering the spectral range of the vidicon sensor. Filters 3, 5, and 7 were polarizing at angles of 0, 60, and 120 degrees, respectively. Filter 2 (orange) was centered at 610 nm, Filter 4 (green) at 545 nm, Filter 6 (blue) at 477 nm, and Filter 8 (violet) at 414 nm. The filter wheel permanently jammed at position 5 during the spaceraft's 118th orbit.

Where to find it

Mariner 9 data is most easily found at the PDS Imaging Node. This data is available in *.IMG format and can be converted with IMG2PNG with no issue. Imaging data is named by the spacecraft clock time, with images taking the code xxxxxxxxx.img. These refer to the number of seconds after a reference time, or "DAS number". If you are using the photo catalogs listed below, refer to the DAS number, not the listed photo ID number. For example, if the DAS number listed in a catalog is 9,845,434, the image will be contained in a PDS folder named 'c098xxxx', and the file name will be 09845434.img.

A word of warning: the data is currently very disorganized in the PDS. Although the archive suggests that the example file given above would be located in data volume mr9iss_0009 (images in the range 09518259 - 13511838), it is actually located in data volume mr9iss_0008, and additional images with a DAS number of ~9,800,000 can be found in data volume mr9iss_0007. So if you can't find an image where the PDS file listing says it should be, dig around the other data volumes. Alternatively, you can download the entire dataset (only a few gigabites in size), and reorganize it on your hard drive. This is the route I took.

Library Documents

The most organized sources for finding observation sequences are through the "Mariner Mars 1971 television picture catalogs". Volume 1 contains a thorough description of the spacecraft imaging system, calibration data, mission phases, image sequence design, and photo locations for selected surface and limb observations. Volume 2 contains an orbit by orbit sequence description up to the spacecraft's 262nd orbit of Mars, the end of the spacecraft's prime mission. The addendum to Volume 2 completes the coverage of the mission until the end of its extended mission at orbit 676.