JWST APT for fixed-slit spectroscopy E. Puga for the ESA SOT team - - PowerPoint PPT Presentation

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JWST APT for fixed-slit spectroscopy E. Puga for the ESA SOT team 28 Aug 2019 ESA UNCLASSIFIED - Releasable to the public Outline for me APT fixed slit spectroscopy templates Target acquisition (explain tradeoffs) Science aperture

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JWST APT for fixed-slit spectroscopy

E. Puga for the ESA SOT team

28 Aug 2019

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Outline for me

§ APT fixed slit spectroscopy templates § Target acquisition (explain tradeoffs) § Science aperture selection § Wavelength coverage and gaps § spectral resolution § sensitivities § Subarray detector configurations + detector readout pattern § Dither pattern (trade offs) + background subtraction

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APT Fixed-slit spectroscopy templates

§ NIRSpec § MIRI

§ Fixed Slits in NIRSpec and MIRI are designed to provide high contrast single object spectroscopy and bright

bject time series spectroscopy.

§ When creating a new observation, the user defines the APT template § APT fixed-slit spectroscopy templates are divided into four sections: 1. Generic information 2. Observation information 3. Target acquisition parameters 4. Science parameters

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APT Fixed slit spectroscopy template

§ NIRSpec

Generic information Observation information

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APT Fixed slit spectroscopy template

§ NIRSpec

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APT Fixed slit spectroscopy template

§ MIRI

§ Dedicated observations for source/ background defined at Target Level

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NIRSpec ETC Calculation for Target Acquisition

WATA New v1.2

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Target acquisition

NI RSpec TA m ethods: § W ATA ( default) using science or offset target centred in S1600A1. 8-15 minutes. Expected accuracy: 20 mas. § MSATA uses a catalogue reference stars (may require pre-imaging). It is specified at the visit level

f the observation, not directly at the observation
template. 24-30 minutes. Expected accuracy: 20 –

60 mas. § NONE is not recommended for FS. The resulting pointing accuracy will be that delivered by the GS acquisition at the start of the Observation. For reference, the absolute pointing accuracy of JWST for NIRSpecis expected to be ~ 0.34 arcsecond § https://jwst-docs.stsci.edu/near-infrared-spectrograph/nirspec-

bserving-strategies/nirspec-target-acquisition-recommended-strategies

MI RI TA procedures: § LRS slit mode § LRS slitless mode § Use of science or offset target, at distance < 60 arcsecond § TA is therefore not mandatory in the LRS APT template; however, for observations of point or compact sources it is highly recommended. § https://jwst-docs.stsci.edu/mid-infrared-instrument/miri-observing- strategies/miri-generic-recommended- strategies#MIRIGenericRecommendedStrategies- MIRI_TA_BPTargetacquisitionbestpractices § https://jwst-docs.stsci.edu/mid-infrared-instrument/miri-observing- strategies/miri-lrs-recommended- strategies#MIRILRSRecommendedStrategies- TargetAcquisitionConsiderations

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Target Acquisition strategies and parameters

NI RSpec: § MSATA: § Filters: F110W, F140X, CLEAR § Subarray configuration: FULL § Readout pattern: NRS, NRSRAPID, NRSRAPIDD1, NRSRAPIDD2 § WATA: § Filters: F110W, F140X, CLEAR § Subarray configurations: SUB32, SUB2038, FULL § Readout patterns: NRS, NRSRAPID § Groups/ Integrations are fixed § TA readout mode switch with respect to science parameters costs extra time. MI RI : § Filters: F560W, F1000W, F1500W, and FND § Subarray configuration: N/ A, controlled by the subarray science parameter § Readout patterns: FAST(default), FASTGRPAVG § Groups are selectable, integrations is always 1

The user should always refer to the ETC for signal-to-noise calculations.

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NIRSpec Science apertures

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NIRSpec Science apertures

§ S200A1, S400A1, S1600A1 with slit sizes 0.2 x 3.2, 0.4 x 3.65 and 1.6 x 1.6 arcsec, respectively § S200A1 and S200A2 in slit combination to cover the gap, that doubles the exposure time § 8 filter-disperser combinations https://jwst-docs.stsci.edu/near-infrared-spectrograph/nirspec-observing-modes/nirspec-fixed-slits- spectroscopy/nirspec-fs-wavelength-ranges-and-gaps

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MIRI Science apertures

§ Low Resolution Spectrometer (R~ 100) § Prime spectrometer for observations of faint targets at 5 – 12 µm § Prism in imager filter wheel § 0.5 x 4.6 arcsec slit or slitless (more stable for high precision spectro-photometry, but less sensitive since no background masking) § Saturation limits (point sources @7.5 µm): slit – 100.3 mJy, slitless – 1324 mJy

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Subarray configurations and Readout patterns

NI RSpec: § Subarray: § FULL § Tailored subarrays per individual slit: SUBS200A1, SUBS200A2, SUBS200B1, SUBS400A1 § S1600 subarrays: SUB2048, SUB1024A, SUB1024B, SUB512 § ALLSLITS (S200A1 and S200A2 combined, but not

nly)

MI RI : § Subarray: § FULL (slit) § SLITLESSPRISM (slitless) § Readout patterns: § SLOW (Nsamples = 9, t 1= 23.890 s) § FAST (Nsamples = 1, t 1= 2.775 s)

https://jwst-docs.stsci.edu/near-infrared-spectrograph/nirspec-observing- strategies/nirspec-detector-recommended-strategies

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FS Nods and dithers

NI RSpec: § APT Primary dither positions = = nod along the slit used to subtract background flux § Sub-pixel dithers used to mitigate detector effects, help remove cosmic rays, and particularly improve spectral and/ or spatial sampling

§ https://jwst-docs.stsci.edu/near-infrared-spectrograph/nirspec-observing-strategies/nirspec-background-recommended-strategies § https://jwst-docs.stsci.edu/near-infrared-spectrograph/nirspec-observing-strategies/nirspec-dithering-recommended-strategies

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FS Nods and dithers

MI RI : § ALONG SLIT NOD (default for compact sources) § MAPPING customizable offsets along-slit and across-slit. Extended sources mapping can also be produced by mosaicing. § In slitless mode, dithering is not allowed

§ https://jwst-docs.stsci.edu/mid-infrared-instrument/miri-observing-strategies/miri-lrs-recommended-strategies#MIRILRSRecommendedStrategies- ditherDithering

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APT Fixed slit spectroscopy template

§ Other tabs: Mosaic properties, Special Requirements, Comments tabs

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APT FS Summary

§ For v27.2, substantial effort has been put into improving ETC-APT handshake § Target Acquisition is currently more complete and setting its parameters requires some decisions and ETC dedicated calculations. § FS Science parameters: § Explore capabilities. Starting point: JWST Pocket Guide § Consider tradeoffs regarding aperture selection, subarray detector configurations and detector readout patterns and especially background subtraction.