IO

Updated 29th September 2011

Introduction

IO (Infrared-Optical) is a replacemet for the RATCam and SupIRCam cameras, providing wider fields of view, improved image quality and the ability to simultaneously image in both the optical and IR bands. The instrument consists of four fundamental components:

• IO:O - an optical imaging camera with a 10x10 arcmin field of view.
• IO:I - a near-infrared (JH) imaging camera with a 6x6 arcmin field of view.
• IO:THOR - a fast readout optical camera with a 4x4 arcmin field of view
• IO:BEAM - a beam stearing system incorporating dichroic mirrors and tip-tilt stages

Current Status

Updated 31st January 2012

• IO:O was fitted to the telecsope in November 2011, and a two month comissioning process undertaken which resulted in significant rework of a number of elements of the system.
• Using the default Aluminium fold mirrors, overall throughput for RATCam and IO:O are the same at r-band. At longer wavelengths IO:O throughput is higher and for shorter wavelengths RATCam wins. We do not recommend using IO:O in u-band at all. For the Bessell B filter we also suggest using RATCam unless the extra field of view is absolutely vital. At B the IO:O throughput is approximately half that of RATCam though of course the sky area covered is four times as large.
• One recent addition not previously advertised is an option to use an over-coated gold feed mirror instead of the Aluminium mirror. This gives roughly 7% better throughput in the I and Z filters but please be aware that its long term future is not assured. It may not be offered again after semester 12A so please consider that for long term monitoring proposals.
• Currently only 2x2 binning (0.303arcsec/pix) is being offered. Full frame 2x2 binned readout time is 17sec so for short integrations of bright sources, RATCam may remain more efficient if you do not require the enlarged field of view. No windowed modes are currently available, although we aim to deploy by mid-Semester.
• IO:THOR is available for use with a single OG515 filter defining the blue response and the CCD cutoff the red response. No dichroic is fitted, so simultaneous imaging with IO:O is not currently supported.

IO:O

Specifications

IO:O is equipped with a large diameter iris shutter. This results in a different exposure time between the centre and edge of the field of 80ms. For resonable photometric accuracy exposure times should therefore be greater than 10-20 seconds.

Filters

IO:O has a single, 12 position wheel. Sloan, Bessell B and V and a set of H-alpha filters are available:

Standards

Regular (every 2-3 hours) photometric standards will be obtained in the broad band filters. The standard fields to be used have not yet been determined.

Sensitivity

The exposure time calculator has been updated with sensitivity estimates based on engineering data. Sensitivity is expected to be similar to RATCam apart from in the u-band (where IO:O should have around 3 times greater sensitivity) and the z-band (where IO:O should be around 2 times more sensitive).

Pipeline

A data redution pipleine similar to that for RATCam will be available

Observing Overheads

These will be similar to RATCam

IO:I

Specifications

IO:THOR

Specifications

Filters

IO:THOR has a single fixed OG515 filter. However the incoming light will have passed through either the "Red" or "Blue" dichroics in the IO:BEAM system, giving two possible passbands ("blue" ~5150 - 6700 Angstroms) and ("red" ~6700 - 9000 Angstroms) where the long wavelength cutoff of the "red" option is defined by the CCD QE cutoff.

Standards

Regular (every 2-3 hours) photometric standards will be obtained in the broad band filters simultaneus with IO:O. The standard fields to be used have not yet been determined.

Sensitivity

Sensitivity should be similar to RATCam.

Pipeline

A data redution pipleine will be available.

Readout Speed

Depending on window size, readout speeds vary between around 0.5 seconds and 0.007 seconds. Fast timing experiments and lucky imaging are theirfore potential applications of THOR. In addition it will eventually serve as a generator of tip-tilt correction signals for the beam being fed to IO:O.

Observing Overheads

If you propose to use THOR, you must consult with the LT team prior to proposal submission in order to determine overheads etc.

IO:BEAM

Specifications

The IO:BEAM system contains a number of mechanisms designed to flexibly route the optical beam to the IO:O, IO:I and IO:THOR instruments in a number of different configurations. The final system will comprise

• A deployable optical/IR dichroic mirror that can be placed in the beam feeding IO:I, allowing optical light to pass through to IO:O and IO:THOR
• A deployable tip-tilt mirror that can be placed in the beam feeding IO:I and used for tip-tilt correction and beam-switching.
• A tip-tilt mirror permanently in the beam feeding IO:O and IO:THOR to be used for tip-tilt correction
• A three position mechanism allowing IO:O to be fed by either a mirror or short or long pass dichroics. When the dichroics are used, the beam will also pass through to IO:THOR.

The current system comprises the final two elements only.

A custom Phase2GUI panel will be provided to control these elements as part of your observing sequence. A screenshot of the prototype is shown below: