# Presentation: 446293

## Hubble Space Telescope Coronagraphs

- John Krist
*JPL*

## HST Cameras with Coronagraphs

- NICMOS Camera 2
-  20” x 20”, 76 mas pixels
-   = 0.9 – 2.2 m, multiple filters
- STIS (will be repaired in next mission)
- 52” x 52”, 50 mas pixels
-   = 0.2 - 1.0 m (no filter)
- ACS High Resolution Camera (HRC)
-  26” x 29”, 25 mas pixels
-   = 0.2 - 1.0 m, multiple filters

## NICMOS Coronagraph

- 76 mas pixels, 20” x 20” field
- Multiple filters over = 0.9 - 2.2 m
- Occulting spot is *r *= 0.3” (1.7 - 3.5 /D)hole drilled in mirror at intermediate focal plane
- Spot and Lyot stop always in-place

## NICMOS Coronagraph PupilModels

- Pupil after spot

- With an Aligned
- Lyot Stop

## Effects of NICMOS Lyot Stop Misalignment

- Aligned Lyot Stop
- Model

- Misaligned Lyot Stop
- Model

- Observed

- F110W (~J band)

- Misalignment results in 2x more light in the wings + spikes

## NICMOS Image of HD 141569F110W (~J band)Science results in Weinberger et al. (1999)

- HD 141569

- Reference Star

- Image1 – PSF1

- Image1 – PSF2

- Image2 – PSF1

- Image2 – PSF2

## STIS Coronagraph

- Primarily a spectrograph
- CCD, 50 mas pixels, 52” x 52” field
- Unfiltered imaging over = 0.2 - 1.0 m
- Occulters are crossed wedges: *d *= 0.5”-2.8” (*r *= 5/D – 30/D @ V)
- Lyot stop always in the beam

## STIS Occulters

## STIS CoronagraphComputed Intensity at Lyot Stop

- After Occulter,
- Before Lyot Stop

- After Lyot Stop

## STIS Image of HD 141569

- HD 141569

- Reference Star

- HD 141569 - Reference Star

- 7”

- Science results in Mouillet et al. (2001)

## ACS/HRC Coronagraph

- CCD, 25 mas pixels, PSF FWHM=50 mas @ 0.5 m
- Multiple filters over = 0.2 - 1.0 m
- Selectable mode in the HRC: the occulting spots and Lyot stop flip in on command
- Two occulting spots: *r *= 0.9” and 1.8” (38/D – 64/D @ V)
- Occulting spots in the aberrated beam from HST, before corrective optics

## ACS Coronagraph1st (Aberrated) Image PlaneModel

## ACS Coronagraph Pupil Models

- Pupil After Spot

- Pupil After Lyot Stop

## ACS Coronagraph Image of HD 141569

## PSF Subtraction

- Beta Pictoris

- Alpha Pic

- Beta - Alpha Pic

- ACS coronagraph
*ACS Science Team*
*(Golimowski et al. 2006)*

- Reference PSF Subtraction

- Roll Subtraction

- Roll 1

- Roll 2

- 1 - 2

## ACS Coronagraph Images of Beta Pic

- Separated by 10 degrees in orientation, 5 hours in time

- 20”

## Spectral DeconvolutionSparks & Ford (2002)Images courtesy of Bill Sparks

- HD 130948 (ACS Coronagraph)

- After Spectral Deconvolution &
- Unsharp Masking

## ACS PSF Mean Brightness Profiles (V)

## ACS Coronagraph Point Source Detection Limits

## HST vs. Ground: HD 141569

- ACS Direct (V)

- STIS Coronagraph (U→I)

- NICMOS Coronagraph (J)

- ACS Coronagraph (V)

- Palomar AO
- Coronagraph (2.2 m)
- Boccaletti et al. 2003
- (Their image)

## HST vs. Ground Coronagraphs

- HST limited to inner radius of r>0.6” (near-IR) and r>0.7” (visible, if STIS repaired, else 1.1” with ACS); on ground, 4/D at 2 m with a 10 m scope is 0.17”
- HST stability allows PSF subtraction providing up to an additional 200x improvement in contrast (coronagraph improves contrast up to 7x); ground scope stability limited in most cases to <10x (PSF subtraction or SDI) and limited AO correction radius
- HST is much better than ground for most disk imaging at radii > 1”; large scopes on ground better for point sources closer in

## Slide 22