Study of NRO Telescopes for WFIRST

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1 Study of NRO Telescopes for WFIRST NRO Telescope Workshop Jeffrey Kruk GSFC September 4, 2012

2 Outline Mission overview Science programs ImplicaKons of NRO telescope capabilikes Open QuesKons Conclusions 9/4/2012 NRO Telescope Workshop - Kruk 2

3 Recent WFIRST History: The WFIRST Science DefiniKon Team has studied two Design Reference Missions Report released Aug 2012; arxiv: Formal studies for 2.4m telescope about to start Science performance has yet to be opkmized Preliminary telescope studies in FY13 New SDT to be appointed The mission will conknue to evolve in response to pressures of natural seleckon 9/4/2012 NRO Telescope Workshop - Kruk 3

4 Mission DescripKon L2 Halo orbit ~ km radius Earth- Sun angle 5 year mission life (3 for DRM2) 10 year consumables DSN for communicakons Data Center at IPAC DSN IPAC Other orbits under considerakon for 2.4m telescope 9/4/2012 NRO Telescope Workshop - Kruk 4

5 Observing Zone: Pitch off Sun Line 360 Yaw about Sun Line ±10 roll about LOS (off max power roll*) * Larger roll allowed for SNe Field of Regard SNe Fields SNe InerKally Fixed Fields must be within 20 of one of the EclipKc Poles, will be rotated every ~45 days +54 GB +126 Keep- Out Zone Observing Zone SNe Fields 9/4/2012 NRO Telescope Workshop - Kruk Keep- Out Zone Can observe InerKally Fixed Fields in the GalacKc Bulge (GB) for 72 days twice a year 5

6 Design Reference Mission 1 1.3m off- axis TMA 9x4 H2RG FPA 144 Mpix 0.18 pixels sq deg ackve area 5 year mission 9/4/2012 NRO Telescope Workshop - Kruk 6

7 CANDELS Wide fields on DRM1 focal plane GOODS- S GOODS- N EGS COSMOS UDS

8 Design Reference Mission 2 1.1m off- axis TMA 7x2 H4RG FPA (224 Mpix) 0.18 pixels sq deg ackve area 3 year mission, fits on a Falcon- 9 9/4/2012 NRO Telescope Workshop - Kruk 8

9 NWNH Enabling Widefield (NEW) telescope 2.4m f/8 opkcal system 2 out of 3 mirrors from TMA telescope Includes metering structure, baffles, aperture door, most of the 6- dof SM actuator system, etc. Dynamic test unit 9/4/2012 NRO Telescope Workshop - Kruk 9

10 2.4m cont. Assumed requirements: MulKple instruments On- orbit servicing NO CHANGES! Three instrument bays are natural fit to exiskng structure. Present wide- field instrument design fits in one such bay. 9/4/2012 NRO Telescope Workshop - Kruk 10

11 2.4m FOV diagram 288 Mpix 9/4/2012 NRO Telescope 11 Workshop - Kruk

12 FILTERS Filter Bandpass z Y J H K W DRM- 1 EffecKve Area (scale by 2.5 for NRO) SN prism throughput is ~5% lower than the filters. 9/4/2012 NRO Telescope Workshop - Kruk 12

13 Bandpass (microns) DISPERSERS Resolving power per pixel Spectral length (pixels) DRM DRM2 2.4m Bandpass (microns) Supernova Prism Galaxy Redshiv Prism Ext d source Resolu=on (km/s/arcsec) Point Source Resolu=on (per pixel) Spectral length (pixels) DRM DRM m (TBD) /4/2012 NRO Telescope Workshop - Kruk 13

14 PoinKng Performance preliminary design requirements PoinKng jixer: < 20 mas rms Revisit accuracy: ~10 mas Limited by sexle Kme Short slews (survey steps): <60s, 30s goal Long slews: 180 in < 10 minutes The antenna is on a gimbal, so no observing Kme is lost to downlink 9/4/2012 NRO Telescope Workshop - Kruk 14

15 Science Program Microlensing campaigns for exoplanet census High- laktude survey Imaging for weak lensing & other programs Spectroscopy for galaxy redshiv survey GalacKc plane survey SNIa synopkc survey Guest Observer program 9/4/2012 NRO Telescope Workshop - Kruk 15

16 Microlensing Observe >2 sq deg of GalacKc bulge Revisit each field every 15 minutes over 72 days Depth: S/N >100 in W149 filter for J(AB)=20.5 For DRM1,2 area was 3.38, 3.51 sq degrees Exposure Kmes were 60s, 110s J(AB) at which S/N=100 in W149 vs. Exposure Time 40s 60s 80s 100s 2.4m NRO m DRM m DRM /4/2012 NRO Telescope Workshop - Kruk 16

17 Microlensing- 2 Mean # stars per Baade OGLE 29 Stanek SWEEPS Jmax / l, b 1.06, , , , GB MCT preliminary catalog courtesy of Tom Brown 9/4/2012 NRO Telescope Workshop - Kruk 17

18 Microlensing- 3 Impact of 2.4m telescope Smaller FoV than DRM1,2 Goes ~1 mag deeper for given exposure Kme Doubles density of stars exceeding S/N reqm t Bexer isolakon of stars at high densikes: 3000 stars / 0.01 bin = 1 star per 3.6x3.6 pixels for DRM1,2 = 1 star per 6x6 pixels for NRO. 9/4/2012 NRO Telescope Workshop - Kruk 18

19 High LaKtude Survey Survey area: 3,400 deg 2 Imaging YJHK to AB=26 (5σ point source) Sampling suitable for weak lensing in J,H,K >30 galaxies/arcmin 2 per band, 40 in combined dataset for DRM1, (25 and 31 for DRM2). Spectroscopy Emission line 7σ flux limit: ergs/cm 2 /sec 4858 galaxies/deg 2 over 1.3<z<2.65 ConKnuum S/N=1 per pix at AB= /4/2012 NRO Telescope Workshop - Kruk 19

20 High LaKtude Survey- 2 Impact of 2.4m telescope Imaging: Keep AB=26 limikng magnitude, reduce exposure Kme from > 90s, and make up for small FoV Don t gain by PM area because of greater readnoise Keep exposure Kme ~constant and go to AB=27 Triples number of usable galaxies to ~90/arcmin 2 K band: one mag shallower, lose enkrely,? Spectroscopy: Likely choose to go deeper rather than faster BUT depends greatly on telescope temperature 9/4/2012 NRO Telescope Workshop - Kruk 20

21 SNIa Survey Two- Ker deep synopkc survey(s) in JHK, R=75 prism: 1.8 deg 2 for z<1.7, 6.5 deg 2 for z<0.8 (2.0,5.9 for DRM2) Imaging: 15σ at peak of light curve Spectroscopy: 5σ across Si 6100Å line 5- day revisit cadence over 1.8 years Ranga Ram Chary WFIR 2012 talk: 1-10 PISN/deg 2 /yr 5σ point- source limikng sensikvity: Low- z area High- z area Single visit CumulaKve /4/2012 NRO Telescope Workshop - Kruk 21

22 SNIa Survey Impact of 2.4m telescope Go ~1 mag deeper for fixed exposure Kme Re- opkmize 2- Ker layout to increase SNe yield Tiers change from low & high to high & higher ~triple number of mid- z SNe Improved angular resolukon provides bexer host galaxy subtrackon If K band is lost, will need some adjustment to observing strategy 9/4/2012 NRO Telescope Workshop - Kruk 22

23 GalacKc Plane Survey Survey deg 2 in YJHK to AB=26 Same Kling strategy as the high laktude survey Impact of 2.4m telescope: Likely similar to the high laktude survey Exposures are already short, so may leave as- is and go deeper Devote extra Kme to recovering K- band depth, if possible 9/4/2012 NRO Telescope Workshop - Kruk 23

24 Open QuesKons Topics to be addressed by new SDT and by upcoming telescope studies What is opkmal pixel scale? Reassess depth vs. area trade for each survey What is the red wavelength cutoff? Orbit trades 9/4/2012 NRO Telescope Workshop - Kruk 24

25 Telescope Temperature NRO Telescope is designed for room temperature operakon. Qualified at T= 250K. OpKcal performance unknown at low temperatures. Nominal WFIRST band pass of microns is viable at 280K. Extension to 2.4 microns is possible with 2x higher background at T=250K. ObsTime (sec) to reach AB=26 5σ (Imaging), or Hα flux 1*10-16 at z=1.8, 6.5σ(SPC) Temp z085 Y106 J134 H168 K211 SpC SpC K K K K K K /4/2012 NRO Telescope Workshop - Kruk 25

26 Orbit trades Sun- Earth L2 is best for science operakons Can manage data volume with high- TRL systems but not much room for growth Geosynchronous orbit under considerakon for servicing Energy cost low for L2 ß > GEO transfer Could bring WFIRST to GEO or robots to L2 9/4/2012 NRO Telescope Workshop - Kruk 26

27 RadiaKon Environment L2: 5 high- energy parkcles/cm 2 /sec A lot more during solar flares, but duty cycle is low GEO: same, plus 3x10 5 e- /cm 2 /sec 9/4/2012 NRO Telescope Workshop - Kruk 27

28 Proton & Electron Intensities AP-8 Model AE-8 Model E p > 10 MeV E e > 1 MeV #/cm 2 /sec #/cm 2 /sec L-Shell 9/4/2012 NRO Telescope Workshop - Kruk 28

29 ~5*10 5 e- /cm 2 1MeV and above* Easy to shield low E ~1cm Al for 1MeV More helps slowly de/dx 90% ionizakon below 4MeV 10% bremsstrahlung Hard to shield Shielding *based on 5- yr avg typical day will be lower 9/4/2012 NRO Telescope Workshop - Kruk 29

30 Summary NRO telescope is more than just a faster version of the 1.1m and 1.3m WFIRST designs. QualitaKve improvements to baseline science programs, and new science possible. Major unknown is the temperature over which the opkcs meet specs. RadiaKon environment of geosynchronous orbit is a significant drawback. 9/4/2012 NRO Telescope Workshop - Kruk 30