WRITING A UKIRT TECHNICAL CASE

The technical case is an important part of your application. UKIRT staff use it to check the feasibility of your observations, to verify that the time request is adequate and to ensure that we can plan our instrumentation schedule to meet your requirements.

Give as complete a target list as you can - put this in the technical case if there is not room in the body of the form. Note that sources above +60 Declination and below -40 declination cannot be accessed by UKIRT (see the sky access page). Of course you should also check whether your source RAs are appropriate for the time of year. Software packages are available to help you schedule your own observations, such as UKIRTrise and OBSERVE for STARLINK users.

UKIRTrise is available at :

uktrise.html

You must include in your case (estimates of) source continuum magnitudes or fluxes, or line fluxes if appropriate. This information is essential for the technical assessor of your programme to check your quoted exposure times. Please quote these values at the intended observing wavelength; a V magnitude is of little use to a technical assessor for a UKIRT proposal. If you are proposing to observe a large sample of sources, make sure that you give the mean and range of values. Please adopt the following guidelines when quoting the brightness of your source.

Extended continuum sources	Flux density in W/m2/µm/arcsec or (m)Jy/arcsec2
Point continuum sources	Flux density in W/m2/µm, (m)Jy or give a JHKLL'M magnitude.
Extended line sources	Flux in W/m2/arcsec2

Finally, make sure that you use consistent units across your sample; it has been known in the past for the brightness of four different objects to be quoted in four different units, which makes the task of the technical assessor far more onerous than it needs to be.

You should state your signal-to-noise requirements very clearly (even if all you say is that you require 2-sigma detections). Of course, a science case which fails to explain why these are the requirements is not complete.

The WFCAM instrument page gives details of the exposure times required to reach the background limit. In this limit your signal to noise will increase as the square root of the exposure time and in proportion to the source flux. When the observation is not background limited the S/N increases linearly with on-chip integration time. for WFCAM this generally only makes a difference for eth shortest-wavelength filters and narrow bands. 

You should estimate exposure times; do not leave it to the technical assessor to show that your programme is technically feasible (or not). It is valid to base your requested time on previous experience; however if you do this, it is your responsibility to demonstrate that the objects being observed previously were similar to those now being proposed, and to describe the weather conditions on the previous run. Two tools will help:

You should specify your programme's seeing requirements in the Technical Case, even if this is simply to state that your programme has no particular seeing criteria. Other weather criteria include cloud/photometric. If you need reasonable transparency but can do without photometric conditions, you should state this clearly and explain how your science will be affected. WFCAM observations are not sensitive to the amount of upper-atmosphere water vapour.