ADONIS Infrared Cameras

Data acquisition system: ADOCAM software

Note: The ADONIS infrared cameras are controlled by the observer using the ADOCAM software. Both cameras and the ADOCAM software are completely independent of the adaptive optics system and the telescope control system.

Available Field Of View

The following ADOCAM figure shows the available field of view, superimposed with the camera field of view.

The size of the available field of view is limited by the movement of the M6 mirror, which in turn is limited by the size of the dichroic. As a result the available field of view is a circle of 30 arcsec radius, centered on the wave front sensor (WFS) center (which corresponds to the reference star).

The size of the camera field of view depends on the chosen pixel scale (see tables below).

It is possible to move the M6 mirror in order to centre the camera field of view anywhere within the available field of view. Remember, the M6 mirror is on the bench and so it is completely independent from the telescope control.

For the example shown in the figure, the camera field of view should be centred on the science target by adding an offset to the M6 mirror. Note that the adaptive optics correction performance decreases with distance from the WFS centre.

SHARPII+ Camera

Sharp II and its prefocal optics were built for ESO by the Max-Plank Institute fur Extraterrestrische Physik.
Sharp II is based on a 256x256 Nicmos III array, and suggested for deep, relatively long integration times images. Sharp II has a fast shutter at the internal cold Lyot stop. It can operate in shutter mode when integration times shorter than 400 msec are required (minimum value 20 msec).

Available Lens scales

Pixel scale	Field of view	Recommended purpose
100 marcsec/pixel	25.6" x 25.6"	Search for faint object, Mapping of large areas
50 marcsec/pixel	12.8"x 12.8"	General purpose
35 marcsec/pixel	8.5"x 8.5´	J, H band, under excellent seeing

Detector and optics

NICMOS 3 Rockwell 256x256 array, HgCdTe
Pixel size: 40 µm
Wavelength range: 1-2.5 µm
Quantum efficiency: 60 % average
Minimum exposure time: 20 ms [shutter mode]
Minimum exposure time: 300ms [standard mode]
Minimum read-out-time: 900 ms
Conversion factor: 9 electrons/ADU
Full detector capacity: 283000 electrons

Narrow Band Filters

**Measured Data**
Filter	Central wavelength [µm]	Resolution	Transmission [%]
Continuum	1.068	107	61
HeI	1.083	135	47
P_gamma	1.093	109	53
Continuum	1.107	138	42
Continuum	1.220	136	56
OII	1.236	137	42
FeII	1.256	105	48
P_beta	1.281	142	56
Continuum	1.296	144	55
Continuum	2.044	120	69
HeI	2.057	147	70
Continuum	2.087	104	64
Continuum	2.099	117	45
H_2	2.121	141	68
Continuum	2.145	126	50

Note: narrow band filters with central wavelength below 1300 nm give ghosts due to unexpected wedges.

Broad Band Filters

Broad Band Filter	Central Wavelength Value (µm)	Bandwidth (µm)	Transmission [%]
J	1.253	0.296	~75
H	1.643	0.353	peak 82
SK	2.154	0.323	peak 91
K	2.177	0.378	peak 76

CVF: 1.3- 2.38 µm. Tunable filter

Spectral resolution: 60. Transmission: 35% @1300 nm ; 70% @1800 nm ; 75 % @2380 nm

Imaging performances

The flexure of the optical bench is 14 marcsec/hr and can limit the integration time (assuming no post-processing shifting. The obtained limiting magnitudes for each band and when the adaptive optics is working are:
- 1 hour exposure time divided in sky/object,
- 1 min/frame integration,
- S/N=5,
- pixel scale 0.05"/pixel.

IR filter	magnitude	Additional condition
J	20.6	50% flux within 0.50"
H	20.4	50% flux within 0.47"
K	19.9	50% flux within 0.31"

Background (mag/arcsec²):

IR filter	mag/arcsec²
J	16.5
H	14.1
K	12.4

Note: we experience non-uniform background due to the relay mirrors/dichroics.

User's Guide

The SHARP User's Guide (1997) is available online and as a gzipped postscript file (210 kB).

Shutter Modes

SHARPII+ has two different operating modes depending on the integration time.
The called normal mode can be used for integration time larger than 300ms.
The other mode actuating a cold shutter (the shutter mode) is recommended for integration time below 300ms.
Do not forget to take into account the read-out time of 700ms when evaluating the time budget for your observations.

Choice of the lens scale:

SHARPII+ has 3 different lens scales: 35mas/pixel, 50mas/pix and 100mas/pix.
- 35 mas/pixel for J, H and SK band under excellent seeing conditions. Using 35 mas/pixel scale with K band, is oversampling, but it is recomended if the 8arcsec field is sufficient.
- 50 mas/pixel for general purpose (J, H ,SK and K band) and when using a Fabry-Perot etalon
- 100mas/pixel for K band, for search of faint object or mapping of large areas.
100mas scale has several disadvantages. First, there is vignetting of about 20 % towards the northern corner of the field of view. Second, in the present configuration the ADONIS field of view is somewhat too small for recording sky frames by moving the ON/OFF mirror. Third, there is an unavoidable ghost between the detector and the filters.

Remanence effect:
We have the usual Nicmos III remanence effect using SHARPII+. To avoid that, wait images have to be taken between different positions of the chopping mirror. This time lost must be included in the time budget estimation.

COMIC Camera :

The Comic camera (see image) is optimized for L and M bands. It may be used also in J-H-K bands, in the case of bright object and fast framing. It has the advantage of a fast frame acquisition [read-out time: 40ms], a deep well capacity and an antibloomming CCD. The prefocal optics may be used with Comic as well.

See, for more information, the September 96 Messenger (p.39) issue about Comic camera performances.

Available Lens scales

Pixel scale	Field of view	Spectral Band
100 marcsec/pixel	12.8"x12.8"	L, L', M
35 marcsec/pixel	4.5"x4.5"	J, H, K', K

Detector and optics

LIR HgCdTe 128x128 array (antiblooming CCD)
Pixel size: 50 µm - filling factor 74%
Cut-off wavelengths: 1-5 µm
Mean quantum efficiency: 60 % at 77 °K
Linear capacity: 5.9·10⁶ e^-
Linearity: between -32768 and 25655 ADU
Pixel Gain Dispersion: sigma of 5% average gain, Gaussian distribution
Conversion factor: 92 electrons/s/pixel
Dark current: 2000 e^-/s/pixel at 77° K
Read-out-noise [in flashing mode]: 1000 e^-
Read-out-time: 40 ms
Minimum exposure time: 10 ms
Maximum exposure time: 640 s (software limitation)
Background limited exposure time in M and L band: 1.5 / 7 s

Narrow Band Filters

Line	Wavelength [µm]	Bandwidth [µm]
H2S(1)	2.126	0.021
H2 continuum	2.181	0.023
PAH	3.296	0.070
PAH continuum	3.057	0.27
H3+	3.526	0.042
H3+ continuum	3.567	0.038
Br alpha	4.045	0.041
Br alpha continuum	3.757	0.386

Broad Band Filters

Broad Band Filter	Central Wavelength Value (µm)	Bandwidth (µm)
J	1.259	0.229
H	1.645	0.332
K´	2.166	0.328
K	2.190	0.409
Lstandard	3.480	0.590
L´	3.809	0.623
M	4.832	0.590

Tunable CVF Filter

- 1.34 - 2.52 µm (resolution 62)
- 2.50-4.52 µm (resolution 120)

Imaging performance

Complete analysis by

Marco, O., Lacombe, F.,Bonaccini, D. 1996, The Messenger, 85, 49.
Lacombe, F.; Marco, O.; Geoffray, H.; Beuzit, J. L.; Monin, J. L.; Gigan, P.; Talureau, B.; Feautrier, P.; Petmezakis, P.; Bonaccini, D. 1998, PASP, 110, 1087 ,"Adaptive Optics Imaging at 1-5 Microns on Large Telescopes: The COMIC Camera for ADONIS"

Point Source	Extended Source
Mag	Strehl %	Mag/arcsec²
mJ = 13.0	30	9.3
mH = 12.5	30	9.4
mK = 11.8	40	9.0
mL = 10.7	50	8.6
mL' = 10.1	50	8.2
mM = 7.7	50	6.3

IR filter	Mag/arcsec²
J	15.5
H	14
K	11.2
L´	2
M	-0.9

IR filter	Zero point (mag)
J	18.6
H	18.4
K	17.8
L	17.7
L´	17.2
M	15.7

User's Guide

The COMIC User's Guide is available as a gzipped postscript file (860Kb).

Integration time in L and M band:
The COMIC camera is optimized for L and M band. In these band, integration time is strongly dependent on the background level.
Comic has a deep well capacity of about 64500 ADU. Observers will have to avoid that the level background + science object reaches 64500 ADU.
Typical background limited integration time on the telescope are about 7s in L band and 1s in M band.

Antibloomming CCD:
Comic Camera is equipped with an antibloomming CCD. Antibloomming system permits to get saturated or very intensive pixels that do not give any consequence on the sensitivity of the other nearest pixels.
This allows to observe the close neighboring of very bright object.

Pattern in the background:
Due to gratings disuniformities on the ADONIS bench, we are suffering of a non-uniform instrumental background. This problem has been partially corrected changing the dichroic in August 97. The patterns won't be the same if you move the ON/OFF mirror. Due to the instability of the background in L and M band, sky subtraction has to be done using the ON/OFF fast moving capabilities, even if different patterns will appear in the images.
One way to get rid of that problem is to be able to evaluate the level of these patterns and subtract them while processing data in your home institute. Therefore, we recommend to do an offset of the telescope and take a few images on the free sky near your object and that for each configuration of the ON/OFF.
This procedure takes no much more than one or two minutes for each object. Please contact the support astronomer to get more information on the faisability of your program proposed with this camera.

Choice of the lens scale:
Two different lens scale are available with COMIC:
- 35 mas/pixel for J, H and K band
- 100mas/pixel for L, L' and M band.
Coatings for lenses have been optimized respectively for each IR band.
So, one should not observe in K band with 100mas pixel scale.

ADOCAM Computer:

The data acquisition system called ADOCAM Computer was built by Observatoire de Paris-Meudon.
The acquisition software is identical for both cameras SHARP II+ and COMIC.

Images are taken by the camera and displayed after Quick Look Analysis on a control screen. Adocam Computer stores raw or processed data in FITS format.

ADOCAM computer controls:

the camera itself, the dewar motors and temperature
the integration set-up (object name, observing mode, sequence...)
acquisition, display and storage functions for data
the ADONIS chopping mirror (ON/OFF)
the prefocal optics settings.

The most important capabilities of ADOCAM computer are:

batch programming for both cameras
programming for ON/OFF pointing
differents chopping modes
Filter sequences including CVF sequences
Fabry Perot sequence (scan through a line)
Polarizer sequence
Quick Look Analyses which permitts basic reductions on frames.
auto-generated log file

User's Guide

A thorough description of the ADOCAM software is given in the COMIC User's Guide which is available as a gzipped postscript file (860Kb).