CIRPASS

The Cambridge IR PAnoramic Survey Spectrograph

Click HERE for access to local CIRPASS Web pages (restricted access only)

 

A simulation of CIRPASS's 500 element Integral Field Unit being used to study an HDF galaxy merger. The spectral resolution is 6-20 times better than COHSI and will facilitate internal  dynamical studies.The example shown here is CFRS 14.1129 in HST F814W. At z=0.831 H-alpha is at 1.202 microns. In this example the fore-optics are arranged to give 0.25 arcsec across each lenslet.

We have recently obtained funds to transform COHSI in to a new spectrograph called CIRPASS and make it available to the GEMINI community on GEMINI-N from mid-2000. To be ready in just over one year from now will require a big effort from our group here at the IoA but we believe it is possible because a large fraction of the system already exists.

CIRPASS will be operated by the IoA for the benefit of observers throughout the Gemini community who will obtain telescope time in the same way as they would for a Gemini Facility Instrument. For every 4 nights allocated the UK community will get an extra reward night.

The main features of the CIRPASS spectrograph are:

· 20482 HgCdTe HAWAII-2 array from Rockwell (a 1024 array will be used if the 2048 array is delayed)
 
· Software suppression with some Hardware OH suppression (c.f. a coronograph) to reduce scattered light and increase the S/N ratio.
 
&middot; Spectral resolution options R<26,000 with typically R~3500 for very faint galaxy programs.
 
&middot; Few optical elements leading to high throughput
 
&middot; Wavelength range 0.85-1.8 microns (0.43 microns in a single hit at ~2.2 Angstroms/pixel)
 
&middot; 500 element IFU with several scale options, biggest FOV 13x5 arcsec
 
&middot; Multi-object feed with 180 fibres and a 6 arcmin FOV
 
&middot; S/N=5 in 3 hours for J~23.2, H~22.2
 
&middot; 7e-19 ergs cm-2 s-1 line fluxes in 3 hours
 
The original form of COHSI used a hardware OH suppression technique because of the relatively small arrays (2, 2562 arrays) which simply do not have enough pixels to capture a large number of spectra at R=3000 and have full J+H spectral coverage. With the advent of the new 10242 and 20482 arrays this restriction is removed and it is possible to do the OH suppression in software (digital suppression) by simply capturing the spectra at high spectral resolution and ignoring the small percentage of pixels hit by OH lines. This is how CIRPASS works.  However, to ensure that scattered light and ghost images do not substantially increase the background above that of the sky CIRPASS employs a hardware mask as well.


CURRENT STATUS OF PROJECT
 
We are currently testing a prototype version of CIRPASS on our local 0.4m telescope. This prototype has a warm camera, a 1024 array and blocking filters borrowed from CIRSI.

 

The data format with the COHSI/CIRPASS prototype. The 63 horizontal white stripes are fibre spectra obtained using a continuum source. Note the uniformity of the IFU. The vertical stripes are due to the blocking lines on the mask.

 

A mosaic of 3 exposures using the COHSI/CIRPASS prototype.The top third shows the spectra of the Mauna Kea night sky with the grating offset so that the OH lines are not blocked at the mask.The middle third shows the mask illuminated directly (not through the fibres). The AR coated mask features are clearly seen.The bottom third shows the suppressed night sky. Some weak oxygen lines which have no mask features can still be seen.

 

 

 

 

 

 

 

 

 

 

 

 

URL http://www.ast.cam.ac.uk/~optics/cirpass/cirpass.htm - Revised: 10 May 99 We are part of the Institute of Astronomy , which is part of the University of fCambridge

CIRPASS - The Cambridge IR PAnoramic Survey Spectrograph

 

CIRPASS

The Cambridge IR PAnoramic Survey Spectrograph

Click HERE for access to local CIRPASS Web pages (restricted access only)

 

A simulation of CIRPASS's 500 element Integral Field Unit being used to study an HDF galaxy merger. The spectral resolution is 6-20 times better than COHSI and will facilitate internal  dynamical studies.The example shown here is CFRS 14.1129 in HST F814W. At z=0.831 H-alpha is at 1.202 microns. In this example the fore-optics are arranged to give 0.25 arcsec across each lenslet.

We have recently obtained funds to transform COHSI in to a new spectrograph called CIRPASS and make it available to the GEMINI community on GEMINI-N from mid-2000. To be ready in just over one year from now will require a big effort from our group here at the IoA but we believe it is possible because a large fraction of the system already exists.

CIRPASS will be operated by the IoA for the benefit of observers throughout the Gemini community who will obtain telescope time in the same way as they would for a Gemini Facility Instrument. For every 4 nights allocated the UK community will get an extra reward night.

The main features of the CIRPASS spectrograph are:

&middot; 20482 HgCdTe HAWAII-2 array from Rockwell (a 1024 array will be used if the 2048 array is delayed)
 
&middot; Software suppression with some Hardware OH suppression (c.f. a coronograph) to reduce scattered light and increase the S/N ratio.
 
&middot; Spectral resolution options R<26,000 with typically R~3500 for very faint galaxy programs.
 
&middot; Few optical elements leading to high throughput
 
&middot; Wavelength range 0.85-1.8 microns (0.43 microns in a single hit at ~2.2 Angstroms/pixel)
 
&middot; 500 element IFU with several scale options, biggest FOV 13x5 arcsec
 
&middot; Multi-object feed with 180 fibres and a 6 arcmin FOV
 
&middot; S/N=5 in 3 hours for J~23.2, H~22.2
 
&middot; 7e-19 ergs cm-2 s-1 line fluxes in 3 hours
 
The original form of COHSI used a hardware OH suppression technique because of the relatively small arrays (2, 2562 arrays) which simply do not have enough pixels to capture a large number of spectra at R=3000 and have full J+H spectral coverage. With the advent of the new 10242 and 20482 arrays this restriction is removed and it is possible to do the OH suppression in software (digital suppression) by simply capturing the spectra at high spectral resolution and ignoring the small percentage of pixels hit by OH lines. This is how CIRPASS works.  However, to ensure that scattered light and ghost images do not substantially increase the background above that of the sky CIRPASS employs a hardware mask as well.


CURRENT STATUS OF PROJECT
 
We are currently testing a prototype version of CIRPASS on our local 0.4m telescope. This prototype has a warm camera, a 1024 array and blocking filters borrowed from CIRSI.

 

The data format with the COHSI/CIRPASS prototype. The 63 horizontal white stripes are fibre spectra obtained using a continuum source. Note the uniformity of the IFU. The vertical stripes are due to the blocking lines on the mask.

 

A mosaic of 3 exposures using the COHSI/CIRPASS prototype.The top third shows the spectra of the Mauna Kea night sky with the grating offset so that the OH lines are not blocked at the mask.The middle third shows the mask illuminated directly (not through the fibres). The AR coated mask features are clearly seen.The bottom third shows the suppressed night sky. Some weak oxygen lines which have no mask features can still be seen.

 

 

 

 

 

 

 

 

 

 

 

 

URL http://www.ast.cam.ac.uk/~optics/cirpass/cirpass.htm - Revised: 10 May 99 We are part of the Institute of Astronomy , which is part of the University of fCambridge