Table of Contents
Latest instrument ground tests have shown that the time spent per grating position in Nyquist sampling and SED mode are too low.
- Implication for the user : observations may produce unusable data.
- Recommended action: A minimum repetition factor of 2 must be entered in HSpot for AORs using range scans in Nyquist sampling and SED modes.
In the range sensitivity plot functionality, the units on the Y-axis can disappear in the line sensitivity plot, after zooming too much.
- Implication for user: sometimes inconvenient when reading the Y scale
- Recommended action: none.
In the three SED modes the reference wavelength is always used in the time estimator calculations, however HSpot does not automatically add a range in the SED mode.
- Implication for user: The user needs to enter range and a reference wavelength in the PACS range editor.
- Recommended action: Use the range sensitivity plot GUI to get the sensitivity at the user desired reference wavelength.
Depth of coverage maps.
The PACS photometer depth of coverage maps are unfortunately offset by about 10 arcmin, as a side effect of the new way of handling instrument apertures in HSpot. This is the same problem as for the AOR overlays.
There is a bug in the computation of the noise rms for spectral surveys performed over a partial range of the available mixer frequency range. The noise temperature used in the computation is estimated on the assumption of a full band survey. This means that noise estimates in areas of potential low Tsys in comparison to the average distribution over the band will be over-estimated. Similarly, the opposite effect can also occur.
- Implication for user: not too serious as the Tsys distribution is usually smooth, with the possible exception of band 5, and in the case of very reduced surveys (some GHz).
- Recommended action: if you run time estimates with a noise goal, the time you effectively need is the one returned by HSpot, divided by square root of the ratio of the Tsys in the limited area by the average Tsys over the band. You can then run the time estimate again, but set the time computed according to the previous correction as the goal constraint.
Time estimation for HIFI AORs may fail with a server error when the system is under heavy load. An "Array Index Out of Bounds" exception is given.
- Implication for user: This is usually a minor inconvenience only. However, if time estimation is to be run for large numbers of HIFI AORs this operation should be carried out with the user present to respond to any errors that may occur, rather than being left to run alone.
- Recommended action: Restart time estimation, either from the beginning, or from the AOR at which the error occurred. The sequencer parameters are cached, so little time is lost even if the entire file is recalculated. However, it is even quicker to select the option of calculating time estimates only from the AOR at which the problem occurred, i.e. for "Out of date AORs".
Mapping (and visualisation) for the HIFI DBS raster map mode is using a position angle which is with respect to the Z axis of the telescope. This should be corrected to giving a PA with respect to north on the sky.
- Implication for user: The position angle and thus visualisation changes depending on the date of observation.
- Recommended action: The is no solution for users right now other than to be aware of the problem, although this bug should be fixed fairly quickly within HSpot.
AOR visibility calculated in HSpot may not agree exactly with the visibility calculated in the Mission Planning System.
- Implication for user: HSpot may over-estimate the visibility window by up to 6 days when close to the limit of permanent visibility. In normal cases the true visibility may be 1-2 days less than calculated in HSpot.
- Recommended action: This is a consequence of an approximation made when calculating visibilities in HSpot. It principally affects observations that are strongly constrained, for example, by setting a very narrow range of orientation angles for a scan. Users should avoid over-constraining observations and should be aware that these are essentially severely time-constrained observations that may not ultimately be schedulable. An urgent fix of this problem is planned.
An AOR overlay will sometimes fail to plot
Implication for user: Sometimes AOR overlays will fail to appear due to the size of background map for AOR overlay being insufficient.
- Recommended action: In order to display the footprint on the sky of PACS photometer AORs , a significantly larger background map that the actual size of the AOR footprint has to be used in most of the cases. For instance to display a point-source AOR of less than 3 arcmin x 4 arcmin in the sky a oversized map of minimum size 0.35 x 0.35 degree has to be used.
![[Tip]](../../admonitions/tip.gif)
Tip Users have found that, as a temporary solution, the overlay can also be added by hand by drawing chords with the distance tool on a background image. If you do this for one image the same overlay is added to all open images.