Level 2 Help for MARSMASK

Input image that the the mask is going to be applied.
Must be 1.

Output file containing masked image data.  The output file
is in the same format as input file.
Must be 1.

The mask to apply. It is expected to be in BYTE format.  

If INVERT is specified, the mask is inverted from the default (so formerly
masked areas are now passed, and vice-versa).

By default, the output label is derived from the mask image.  That's because
the mask is generally made from the same input file, so using it means the
mask program (marsfilter or marsdispcompare) is included in the history label.
However, if the mask does not have a proper label, or is otherwise
inappropriate, -IMAGE will cause the label to be derived from the input image
instead.

The DATA_SET_NAME typically identifies the instrument that acquired the
data, the target of that instrument, and the processing level of the data.
This value is copied to the output label, property IDENTIFICATION,
keyword DATA_SET_NAME.

The DATA_SET_ID value for a given data set or product is constructed
according to flight project naming conventions.  In most cases the
DATA_SET_ID is an abbreviation of the DATA_SET_NAME.
This value is copied to the output label, property IDENTIFICATION,
keyword DATA_SET_ID.

When a data set is released incrementally, such as every three months during
a mission, the RELEASE_ID is updated each time part of the data set is released.
For each mission(or host id if multiple spacecrafts), the first release of a data
set should have a value of "0001".
This value is copied to the output label, property IDENTIFICATION,
keyword RELEASE_ID.

Specifies a permanent, unique identifier assigned to a data product by
its producer. Most commonly, it is the filename minus the extension.
This value is copied to the output label, property IDENTIFICATION,
keyword PRODUCT_ID.

Specifies the unique identifier of an entity associated with the
production of a data set. This value is copied to the output label,
property IDENTIFICATION, keyword PRODUCER_ID.

Specifies the identity of a university, research center, NASA center or other
institution associated with the production of a data set.
This value is copied to the output label, property IDENTIFICATION, keyword
PRODUCER_INSTITUTION_NAME.

Specifies a target.  The target may be a planet, satelite, ring, region, feature,
asteroid or comet.  This value is copied to the output label, property
IDENTIFICATION, keyword TARGET_NAME.

Specifies the type of a named target. This value is copied to the output
label, property IDENTIFICATION, keyword TARGET_NAME.