[ldd-ctli] Add value 'Multispectral Imager' to valid values for ctli:type

[sslavney]

Issue Type Enhancement

Describe the issue identified (if applicable) The Lunar Trailblazer mission carries the Lunar Thermal Mapper (LTM) instrument, a multispectral imager. None of the existing values for Instrument/Type/ctli:Type_List/ctli:type is suitable for this instrument's context product. The Lunar Trailblazer Principal Investigator asks to have 'Multispectral Imager' added as a valid value for instrument type.

Describe the solution you'd like We would like to have 'Multispectral Imager' added as a valid value for ctli:Type_List/ctli:type. A definition is provided below under Additional Context.

Describe alternatives you've considered We have considered existing values for ctli:type, but none of them is suitable for this instrument.

LDD Dictionary Version n/a

PDS4 IM Version n/a

Need-by Date This is not urgent. Lunar Trailblazer will probably launch in early 2025. Label development work is underway now. Having this available in the fall 2022 IM release would be sufficient.

Additional context Definition/justification from Bethany Ehlmann, Lunar Trailblazer PI:

"A mulitspectral imager records light in the spectral dimension as well as spatial dimension. A multispectral instrument records radiance as a function of wavelength at each spatial position over multiple discrete wavelength ranges spanning a substantial portion of the electromagnetic spectrum. A multispectral imager may have no visible imaging channels and may operate solely in the UV or infrared. In the case of LTM, LTM acquires 15 spectral channels of data solely in the thermal infrared using an 2D array detector, allowing later reconstruction of a multispectral image cube.

The main difference between and "imager" and a "multispectral imager" is that an imager acquires grayscale or color data per pixel whereas a multispectral imager spans many discrete spectral channels (>4 and typically >10), including wavelengths outside the visible, typically with sufficient spectral breadth and resolution to allow study of not just morphology but composition and/or temperature.

The main difference between a multispectral imager and an imaging spectrometer is the number of bands and how narrow the bands are. Imaging spectrometers acquire hundreds of narrow bandpasses whereas multispectral imagers acquire 4+ wider band passes.

The main difference between a multispectral imager and a radiometer is that the spatial resolution of hundreds of pixels recording the spectral channel in a fixed array allows an image of any or combinations of the multispectral channels to be constructed from the data."

[sslavney]

@lylehuber Any progress on approving "Multispectral Imager" as an instrument type? I would like to finalize this one way or the other so I can submit the context products for the Lunar Trailblazer mission.

[lylehuber]

Waiting on Mark Bentley to return from vacation so that the steward team can discuss.

[sslavney]

Pinging again... I know I marked this non-urgent, but I would like to wrap up the Lunar Trailblazer context products before I leave on June 30, and this issue is holding us up. If we need to revise the definition or pick another value, I would like to know soon. Thanks.

[jordanpadams]

@lylehuber ☝️

[lylehuber]

Susie,

The CTLI Steward Team met to discuss your request for including “Multispectral Imager” as an instrument type. Our opinion is that the distinction between multispectral imager and imaging spectrometer is too narrow to justify having separate instrument types. Recall that the point of instrument type is to facilitate search. Any search across PDS for “Multispectral Imager” should also be expected to return all “Imaging Spectrometer” results so why confuse the issue with separate values? Additionally, an instrument can have multiple types (through the Type_list class), so this instrument could potentially list both “Imager” and “Imaging Spectrometer” as types.

Lyle Huber CTLI Steward Team Chair