Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.stsci.edu/institute/conference/acs_hls/clampin.pdf Дата изменения: Tue Mar 28 20:26:09 2006 Дата индексирования: Sat Dec 22 15:45:31 2007 Кодировка: Поисковые слова: m 35


Design goals: I
· Deep, survey imaging
­ Optimized for near-infrared imaging ­ Wide field, sharper images ­ Survey capabilities ­ imaging ­ low resolution spectroscopy Discovery Efficiency = QE x Area = 10 x WFPC2

· High resolution imaging
­ Optimized for near-UV (200 ­ 400 nm) ­ High angular resolution images ­ High contrast coronagraphic imaging

· Far Ultraviolet Imaging
­ Solar Blind Imaging
­ Low resolution spectroscopy


WFC Optical Design
· Wide Field Channel (WFC)
­ ­ ­ ­ ­ Silver mirror coatings Optimized for I band 202" x 202" field of view 0.05"/pixel plate scale 380 nm - 1050 nm


HRC/SBC Optical Designs
· Solar Blind Channel (SBC)
­ ­ ­ ­ Optimized for FUV band 35" x 31" field of view 0.032"/pixel plate scale STIS flight spare FUV MAMA

· High Resolution Channel (HRC)
­ ­ ­ ­ Optimized for NUV band 26" x 29" field of view 0.025"/pixel plate scale Stellar Coronograph mode


WFC/HRC Filter Wheel 2


WFC/HRC Filter Wheel 1


WFC/HRC Filters: Broadband
­ Sloan Digitial Sky Survey: g, r, i, z

­ WFPC2 filter set: B, V, R & I ­ Deep Imaging: F606W & F814W

­ Near-UV: F220W, F250W, F330W


WFC/HRC Filters: Narrowband
Narrowband
­ WFC: H, [OIII] ­ HRC: NeV, CH4

Ramp filters: ~40"x70" FOV
- 2%: 371-1061 nm

R~100 Grism/Prisms
­ ST-ECF will support ACS grism/prisms


WFC Grism

Pirzcal et al. ST-ECF Tsvetanov, ACS-IDT


WFC/HRC Performance
WFC Pi xel size Chi p pixel format Ful l wel l Dark current at -79oC Quantum Efficiency 400 n 500 n 600 n 700 n 800 n 900 n 950 n 1000 n A-D r ead noi se B-C r ead noi se
WFC Throughput (including OTA
45% 40% 35% 30% 25% 20% 15% 10% 5% 0% 350 5% 400 500 700 Wavelength (nm) 600 0% 200 250

98242MABR10-01 (A-B) 98242MABR10-02 (C-D) 15 µ m x 15 µ m 15 µ m x 15 µ m 2048 x 4096 2048 x 4096 77000 e77000 e6.2 e-/pix/ hr m m m m m m m m 65% 68% 74% 74% 62% 37% 24% 13% 4. 9 e4.9 e7.0 e-/pix/ hr 66% 70% 76% 75% 60% 36% 23% 12% 5.3 e5.0 eWFPC2 STIS WFC#1 WFC#2

HRC Pi xel size Pi xel for mat Fu l l wel l

7161lxd01-01 21 µ m x 21 µ m 1024 x 1024 159, 000 e-

Dar k current at -82oC9. 5 e-/pi x/ hr Quantum Effici ency 250 n m 35% 300 n m 36% 350 n m 39% 400 n m 47% 500 n m 59% 600 n m 63% 700 n m 62% 800 n m 50% 900 n m 35% 1000 n m 14% Read Noi se (A-B) 4. 1 e-, 4.1 eRead Noi se (C-D) 4. 1 e-, 4.4e30% 25%

WFPC2 STIS HRC

Throughput (%)
800 900 1000

20% 15% 10%

300

400

700 Wavel ength (nm)

500

600

800

900

1000


ACS Imaging Performance: I
Limiting AB magnitudes (extended sources)
­ S/N=10, Aperture = 0.2 Sq arcsecs, 2 x 1200 sec images

F F F F

450W 555W 606W 814W

WF PC2 25.78 26.25 26.55 25.81

F F F F

435W 555W 606W 814W

WF C 26.61 26.62 27.20 26.77

HRC 26.02 25.89 26.54 25.79

Limiting AB magnitudes (point sources)
­ S/N=10, 2 x 1200 sec images ­ Apertures: WFC 5x5 pixels, HRC 9x9 pixels, WFPC2 5x5 pixels

F F F F

450W 555W 606W 814W

WF PC2 25.23 25.53 25.74 25.05

F F F F

435W 555W 606W 814W

WF C 26.77 26.65 27.10 26.65

HRC 26.41 26.22 26.77 26.05


ACS Imaging Performance: II
Template Observation: WFPC2 Hubble Deep Field South
­ Limiting AB magnitudes, S/N=10, Aperture = 0.2 arcsec
Limi ting AB Exposure Number Magnitude Time (s ecs) Readouts HDFS_F450W 27.7 101800 51 HDFS_F606W 28.3 97200 49 HDFS_F814W 27.7 112200 56
2

Case 1) HDFS limiting magnitudes
F435W_T exp_HDFS F606W_T exp_HDFS F814W_T exp_HDFS WF C 23663.1 38310.8 29650.6 HRC 41016.9 46994.6 93437.5

*Nreads =20

­ ACS can do HDFS in a third to a quarter of the time Case 2) Expose for Texp~100000 secs (Nreads=50)
F435W F555W F606W F814W WF C 28.60 28.43 28.83 28.38 HRC 28.18 27.95 28.44 27.74


WFC Overheads
Primary overhead driver is onboard memory ­ 34 Mb of CS buffer memory (drives buffer management) ­ WFC images (2068 x 4164) requires 33 Mb ­ HRC images require (1068 x 1044) 2.1 Mb WFC
­ (texp > 340 secs)

· observation overhead: 240 secs · subsequent observations: 150 secs
­ (texp < 340 sec)

· include 340 secs for buffer dump · short WFC exposures incur overhead penalty HRC ­ observation overhead: 150 secs ­ subsequent observations: 60 secs · identical exposures (CRSPLIT or Patterns) ­ 16 observations before buffer dump


WFC/HRC Overheads
-- CRSPLIT exposures of 1200 secs
Observation Setup Overhead CCD readout Buffer dump

-- Example: 3 CRSPLIT exposures of 120 secs
Observation Setup Overhead CCD readout Buffer dump


Auto-Parallels
Auto-Parallels: internal parallel WFC and HRC exposures ­ Constraints · no filter choice · exposure time limited by ­ primary exposure time ­ texp > ~500 secs ­ buffer management constraints · Auto-Parallels are inserted automatically


Auto-Parallels
(1) WFC Primary: 2 x 1000 sec F814W F250W F606W F555W WFC HRC

(2) HRC Primary: 2 x 1200 sec F220W F435W F555W F606W WFC HRC