Note that, in general, 3-bit is less sensitive to lines for a given time and requires more overhead time. Bandwidths up to 2048 MHz cause the calculator to default to 8-bit samplers, although 3-bit sampling may be selected if desired. If the bandwidth is wider than 2048 MHz, the calculator will automatically set the samplers to 3-bit, with 8-bit not selectable. Digital Samplers : 3-bit or 8-bit can be selected.If the bandwidth divided by the frequency is greater than or equal to 0.25, a range of beam sizes is shown that correspond to the range in frequencies. Approximate Beam size: This is the approximate synthesized beam size which is based on the frequency, the configuration selected, and the type of weighting.
The online dopset tool can be used to convert rest frequencies to on-the-sky frequencies at the VLA for certain observing dates.
Representative Frequency : the observing frequency (not the rest frequency) that determines the observing band. Robust (= 0) imaging gives somewhat less sensitivity but a somewhat smaller and better beam as compared to Natural. Natural weighting is usually used to obtain the best sensitivity and a larger, somewhat worse beam, in terms of angular resolution and sidelobes. This affects the RMS noise sensitivity and the beam. Type of Image Weighting : this is the weighting of the data in the u-v plane during imaging. Typical value would be dual for Stokes I flux (density) measurements. Polarization Setup: either single or dual polarization products. See the Calibration section in the Guide to Observing with the VLA for more information. For RMS calculations per baseline (e.g., for calibration) enter 2 for the number of antennas. #Bit resolution calculator full
Number of Antennas : many use 25 instead of the full total 27 antennas to allow for the contingency that not all telescopes are in working order. Array Configuration (A, B, C, or D) : does not affect the RMS noise, but does indicate the brightness temperature sensitivity as well as the confusion level that will be reached (see the OSS for further discussion of confusion). The following screenshot shows the various fields, a description of which is included further below. By hovering the mouse over some fields, a tool tip with some helpful information is shown. After entering data into a field a carriage return, a, or a mouse click outside the input field will submit the data to the calculator. The fields labeled Representative Frequency and then Bandwidth must be entered before the calculator will do anything else. The calculator essentially solves the image noise equation given in the Sensitivity section of the VLA Observational Status Summary (OSS). given time on source, RMS noise required, image weighting, number of polarizations, and sky frequency the ECT will return bandwidth. given time on source, bandwidth, image weighting, number of polarizations, and sky frequency the ECT will return RMS noise. given bandwidth, sky frequency, image weighting, number of polarizations, and RMS noise required the ECT will return time on source. The Exposure Calculator performs the following three types of calculation: Please make sure you use the latest web-based version of the calculator. If you have an old JAVA version of the exposure calculator, please discard it and do not use it. 
The VLA Exposure Calculator is a web-based tool ( ) to help observers to perform these approximate calculations.
The total time a proposer requests has to include not only the time on the sources of interest, but also time spent observing calibrators, slew time between sources, and various types of setup times. The VLA observer is responsible for observing all calibrators required to properly observe as well as calibrate the data after observation in the allocated telescope time.
eXtra-Large Proposals Expressions of Interest.
0 kommentar(er)
