msi2isis

This program will import raw images, acquired from the Near Earth Asteroid Rendezvous - Shoemaker (NEAR Shoemaker) mission's Multispectral Imager (MSI) instrument, to ISIS data file format. The raw image must be in FITS (Flexible Image Transport) format and have a PDS label file that points to the location of the FITS image. You must input either the label file or the FITS file for the "TO" input parameter. Projected images are not supported. Please note if the FITS file is given, the label file must exist in the same directory or the program will throw an error. This program will verify that the input files are valid by checking the following label keyword values. An error will be thrown if any of these criteria are not met.

• INSTRUMENT_ID = MSI
• LINE_SAMPLES = 537
• LINES = 244
• SAMPLE_DISPLAY_DIRECTION = RIGHT
• LINE_DISPLAY_DIRECTION = UP

The output cube- successfully imported into ISIS goes through the following processes:

• Convert the raw FITS image data to an ISIS cube.
• Save the labels from the input PDS label file to the output ISIS cube. Note that FITS labels are not transferred.
• Enlarge the image from 537 samples x 244 lines to 537 x 412 using the user-specified interpolation algorithm. Defaults to cubic convolution.
• Flip the image vertically, i.e. across the horizontal axis.
• Trim 33 pixels from the top, bottom, left and right sides. These pixels along the borders will be set to nulls.

Image Trimming

Shortly after orbit insertion around Eros, the NEAR spacecraft experienced a failed burn that contaminated the MSI instrument with hydrazine. The NEAR/MSI team developed a preliminary remediation [1] of the blur effect of the contamination using FFTs to correct the point spread function (PSF). A residual side effect of this correction was degradation of ~33 pixels on all edges of the images. As a result, by default, NEAR/MSI images are trimmed 33 pixels around all edges after import. MSI images requiring trmming of these data are of the form m0132069107f4_2p_iof_dbl.img.

Additional remediation work of the PSF function used to correct MSI images was performed by Golish [2] that resulted in an enhanced PDF correction that did not introduce edge-artifacts as was seen in [1]. The TRIM parameter was added to optionally retain the 33 pixels around the image edges when the dataset from [2] is used. File names that do not require trimming are of the form m0132069107f4_2p_iof_gbl.img (note the gbl).

Note the images produced by Golish [2] have already been expanded. So msi2isis was altered to check for the expanded size (in lines only) to allow for the full frame to be ingested. In this case, the intermediate step to interpolate in the line dimension to expand the the number of lines from 244 to 412 is not needed and excluded from ingestion processing. All other (label) checks were left to complete the validation of the input files.

References

1. Li, H., et al. (2002) Preliminary Remediation of Scattered Light in NEAR MSI Images. Icarus 155, 244-252. https://doi.org/10.1006/icar.2001.6745

2. Golish, D.R., et al. (2021) Improved Remediation of NEAR MSI Images of Asteroid (433) Eros. LPSC LII, Abstract #1682.

This example shows how to import an MSI fits file to the ISIS cube format using the label file.

msi2isis from=msi_raw_file.lbl to=imported.cub

GUI Example

The application's GUI Example with parameters set to import MSI raw image to a cube.

Raw image

Original image Parameter Name: FROM Example of raw NEAR MSI image without the enlarge, flip, and trim processes performed by msi2isis.

Imported cube

Imported NEAR MSI cube Parameter Name: TO Example of imported NEAR MSI image with the enlarge, flip, and trim processes applied.