Science Concept for Additional Functionality in the Mosaic Planning

Tool

Jeff Valenti

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Current Mosaic Tool in APT

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Mosaic Pattern Definition in APT

Initial mosaic definitionSpecify tiles per row, row overlap, row shift

Specify tiles per column, column overlap, column shift

Specify orientation

Customize a mosaicShift tiles

Rotate tiles (may imply different scheduling window)

Delete tiles

Aladin provides a visual interface[ Initially delivered in APT 20.4, Oct 2012 ]

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Two Motivations for Additional Functionality

UsabilityUsers typically want to map a specific region of the sky, regardless of orient. Existing implementation changes sky coverage as orient changes. [Jen Lotz]

Assessing guide star availability at different orients is tedious with current design

Scheduling flexibilityMosaics are specified at a fixed orient, which implies a narrow scheduling window as one approaches the pole.

The SOC would like to be able to schedule or reschedule mosaics without additional input from the observer. Existing plan is to assign users a new orient and wait for them to submit a revised mosaic specification. That is fine if relatively few mosaics need to be updated.

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Mosaic Usage in the SODRM 2012

SODRM 2012 analysisCaveat: May not be fully representative of actual mission

Over a third of observatory time allocated to mosaics

53% of NIRCam time is mosaics

71% of MIRI time is mosaics

Imaging and IFU mosaics

May be difficult to initially schedule (and in some cases reschedule) a large number of mosaics with fixed orients

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Proposed Mosaic Tool Features

Automatically place tiles for an assumed orientEnable user to define a region of interest on the sky

Enable user to define points that must not be imaged

Proof of concept algorithm does a good job placing tiles

Explore feasibility as a function of orientAssess guide star availability for all tiles at all orients

Determine fixed number of tiles for any orient

Enable change of orient without new observer inputSimplifies operations, perhaps significantly

See JWST-STScI-003431 by Soderblom et al. (2013)“Recommendations for user tools to support mosaics with JWST”

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Proof of Concept Code

[ show movie ]

A region is a bounding polygon with optional holes

Simple algorithmTry to cover region with {rows, columns} of tiles

Each {row, column} can have a different number of tiles

Each {row, column} can have a different offset

For each orient, choose whichever uses fewest tiles

Two passes in the proposal phasePass 1 – find number of tiles to cover entire region

Pass 2 – fixed number of tiles, measure coverage

User indicates orients when automatic tiling is acceptable

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Next Steps

Explore exception handlingHandle tiles with inadequate guide star availability

Avoid any user-specified sky points

Develop engineering conceptChallenging for long range plan (LRP) to handle targets (tiles) with RA and Dec that change with time and jump when tile configuration changes.

Send comments to Valenti, Blair, Soderblom, ...