Frequently Asked Questions
- Answer: Yes. The Observing Programmes Committee (OPC) allocates total time = integration time + all standard operational overheads. To estimate your operational overheads, see the individual instrument User's Manuals and/or use the Execution Time Report function in the P2PP tool.
- Answer: You should assume that your science OBs will be executed completely independently of each other, possibly on different nights, and take into account that no calibration OB will be executed more than once. You should submit enough special calibration OBs to cover that situation. Example: if you need to observe and flux-calibrate six targets in a filter that is not supported in the calibration plan of the instrument, you need to provide six special calibration OBs to allow for the case in which each target is observed on a different night. This must be done so even if the same calibration star can be used for all the science targets. For assistance, contact the User Support Department (email@example.com).
I already installed P2PP on my computer when I prepared Phase 2 material for a previous Period. Do I need to install the latest version to prepare my OBs for the current Period, or will the version I have work?Answer: So long as your observing run is for a La Silla instrument and the version that you used in the past was version 2.13.1 you do not need to re-install P2PP. If you have used an earlier version you must download and install version 2.13.1 for La Silla observing run. If your observing run is for Paranal (VLT, VLTI, VST or VISTA) then please download the latest version of P2PP3.
Can I specify different observing constraints(e.g. seeing, transparency) at Phase 2 than I specified in my Phase 1observing proposal?Answer: You can relax your constraints to increase the chances of execution of your OBs (for example, if you specified Seeing = 1.0 or better at Phase 1, you can specify Seeing = 1.2 or better at Phase 2). However, more stringent constraints (like Seeing = 0.8 at Phase 2 in the previous example) are not allowed, as an essential ingredient of the long-term scheduling of Service Mode programmes over the semester is the constraints that users of approved programmes specified at Phase 1.Allowing more stringent constraints at Phase 2 would thus endanger the completion of even the highest ranked programmes. An allowed exception to this are OBs needed to flux-calibrate observations that can be mostly done under non-photometric conditions, provided that accurate flux calibration is needed for the scientific goals of the programme and that the execution time under photometric conditions does not exceed 20% of the allocated time.The values in the OB constraint sets that are selected (and approved)during Phase 2 preparation (and review) cannot be changed later during the observing period.This is explained in more detail in the Phase 2 Service Mode Guidelines web pages.
I received the notification of time allocation, but when starting P2PP my new program does not appear among the foldersAnswer: Unless you have rebuilt your P2PP installation from scratch, the list of your scheduled runs is not updated every time you start P2PP (note that this applies also if you installed a new version of P2PP but kept the existing local cache; see the P2PP User Manual for details). Thus, when you need to work on new runs using an existing P2PP installation, you need to click on the Download/refresh Observing Runs option under the File menu in P2PP. This will create a folder for each newly approved observing run.
- Answer: The P2PP ID and password now correspond to the ESO User Portal username and password of the Principal Investigator (PI). This is the same username and password used to check Webletters, etc. If you are the PI of a program that has received observing time but you have forgotten your User Portal username and/or password please use the appropriate corresponding link(s) on the User Portal login page.
If you have no accepted programs as PI but wish to learn the use of P2PP, you can use the tutorial account (ID '52052', password 'tutorial') set up for this purpose.
After reviewing my Phase 1 proposal, I have realized that I can observe a better set of targets than the ones I listed then. Since the scientific goal is the same, can I simply change the list of targets?
Answer: In principle, no. The reason is that the allocation of time in Service Mode is a complex process in which one of the main ingredients is the pressure factor on each right ascension interval, derived from the distribution in the sky of the targets that the accepted programmes proposed at Phase 1. The Long Term Schedule that results from the time allocation process would thus be invalidated if changes of target were allowed at Phase 2, this is, after the time allocation has been made.
It is however possible to accept a limited number of target change requests in cases for which a sound scientific justification exists, such as the existence of new observations that demonstrate that a given object of the original sample had been misclassified and is not relevant to the purpose of the programme any more. Target change requests are reviewed by ESO to ensure the strength of the justification and also that there is no other approved programme that intends to execute observations of the new target in a similar configuration.
Target change requests must be addressed to the ESO User Support Department via a dedicated Target/Instrument Setup Change web form.
- Answer: Use Check-out... in the P2PP main window File menu. This will give you access to the ESO Database Browser, where you can use different selection criteria to display your OBs. Once you have highlighted the relevant OBs, you can check them out by choosing theCheck out option in the ESO Database Browser Filemenu. A more detailed description of this procedure can be found in the webpage dedicated to the OB Resubmission Procedures. For users of the new P2PP version 3 tool there is a video tutorial explaining how to check-out individual OBs and OBs within containers. It is important to notice that when OBs are within containers, both check-in and check-out have to be done for the container (i.e. select the container, not its children OBs).
I have an accepted proposal which consists of a pre-imaging run and a follow-up multi-object spectroscopic (MOS) run. May I submit only the pre-imaging OBs now, by the Phase 2 deadline, and the spectroscopic OBs later?Answer: Yes, you should submit only the pre-imaging OBs (i.e. no dummy MOS OBs should be submitted at the general Phase 2 deadline). ESO will make every possible effort to execute all pre-imaging as early as possible, and will release pre-images immediately. In effect all pre-imaging OBs will be treated as ``carry-under OBs'', meaning that they will be executed as soon as they are ready, even if that is before the period starts. For the Phase 2 proposers this means that it is important to submit pre-imaging OBs as soon as possible, even long before the deadline. The earlier valid OBs are submitted, the earlier the pre-images will be taken, and the higher the probability that follow-up MOS observations will be completed within the narrow window of opportunity.
- Answer: We discourage you from doing it. User support astronomers have other professional commitments that sometimes cause them to be away and have limited access to email and, especially, to the tools used in ESO operations, which may cause delays in addressing problems. If you send your request to firstname.lastname@example.org we will ensure that it is always given prompt attention by an expert on the instrument that your run uses, even in periods when your contact scientist cannot deal with it.
I submitted a Waiver Request and it was granted, but I still get the same errors related to the request when I verify my OBs in P2PP. What is wrong?Answer: The short answer is nothing, this is normal. The reason is that the error condition that was waived as a result of your request being approved will be ignored by the receiving application in Garching when you check in your OBs. There is no mechanism available to "tell" your P2PP application to similarly ignore the error.
- Answer: The UTs have a pointing accuracy of 3 arcsec RMS. The expected tracking accuracy under nominal wind load is 0.1 arcsec RMS over 30 minutes when field stabilization is active. The UTs also have the capability of tracking targets with additional velocities (e.g. Solar System targets) under full active optics control. Proposers who need this capability should specify the additional velocities in RA and Dec for their targets. Please check here for further details on UTs performances
My run can be executed more efficiently if my OBs are executed one after another, skipping the acquisitions for the latter OBs. Why cannot I ask for such a procedure for service observing?Answer: There is no guarantee that user specified conditions will last long enough to complete any given OB sequence. Furthermore,breaking down a sequence of OBs often improves overall operations efficiency by allowing the execution of OBs best matching the external conditions. Therefore, to maintain the flexibility needed to adapt to changing observing conditions and to maximise operations efficiency,ESO requires that all Service Mode OBs be treated as independent observations with independent acquisitions. As long as you have requested enough overhead time at Phase 1, there is no penalty to your run.
Having to split my OBs to make them compliant with the rule that no Service Mode OBs could last longer than one hour implies much more execution overhead. Wouldn't it be more efficient to allow longer OBs?Answer: Experience has shown that longer OBs make Service Mode observing less efficient, rather than more. The reason is that, the longer an OB, the more likely it is that the external conditions go outside the acceptable range specified in the Constraint Set. Since OBs executed outside constraints must be rescheduled and re-executed, longer OBs imply not only a higher fraction of OBs to be re-executed, but also a larger amount of time wasted in the execution of OBs failed because of the degradation of external conditions.
Still, some programs require OBs longer than one hour to be scheduled. In such case, a waiver request justifying the need for a longer execution time must be submitted to ESO. When sufficiently justified, these requests are accepted under the condition that the OB will be considered as executed within constraints even if the conditions degrade after the first hour of execution.
If my programme cannot be completed by the end of the Period, can I ask to have it carried over to the next one?Answer:If your programme obtained a Priority Class A and has not been completed by the end of the Period, it will be normally considered as a candidate for carryover to the next Period without you having to request it.This is not possible at present with Priority Class B or C programmes, which are terminated at the end of the Period regardless of their status of completion. Please see our page on the philosophy and scheduling of Service Mode programmes for more information. If you had a Class B or C Programme and you see that the end of the Period is approaching without it being near completion, you are strongly encouraged to resubmit it as a new observing proposal.
- Answer:A key feature of the flexible scheduling approach followed at the ESO Observatories is that Service Mode Programmes do not have definite dates assigned to them. Rather, they are executed according to the external observing conditions, some of which are unpredictable, like the sky transparency or the seeing. Only in this way it is possible to ensure that each of the many programmes approved every semester in Service Mode is executed under the conditions that are necessary for its scientific goals.
ESO has communicated me the allocation of time to my run, but only in class C. Is it worth that I prepare any Phase 2 material at all?Answer:Yes! ESO selects class C programmes from those that did not get a high enough rating to be above the time allocation cutoff line, but whose constraints made them schedulable under a very wide range of conditions (i.e., in intervals of bad seeing, with moon, or under poor sky transparency conditions). Higher rated runs normally have more stringent constraints and, when the conditions are below average, only class C runs may be executable. Due to the high pressure factor at ESO telescopes, the scientific quality of class C runs is normally still very high, and experience shows that Service Mode class C programmes, which would not have been scheduled in classical Visitor Mode, have produced very valuable scientific results.
- Answer: Nothing. A special data quick-release process is in place and you should be contacted with instructions about how to retrieve your data as soon as they are available, usually the next working day.
I have seen in the Run Progress Reports web pages that some data have been obtained for my programme. Can I obtain the data already?Answer: Yes! As of 01 April 2008 Principle Investigators can download their proprietary raw data from the Science Archive Facility as soon as the data have been ingested into the archive. For complete details, including important details regarding the proprietary period for the data see the Data Release page.
- Answer: Until October 2011 the PI-packs accessible via User Portal account contain raw data, associated calibrations and pipeline products. For observations taken after October 2011 ESO no longer provides PI-packs. The raw data can still be accessed via the archive and the associated calibrations and ancillary files are available for download via CalSelector archive service.
Frequently Asked Questions related to X-SHOOTER
- Answer:In X-Shooter the acquisition is done through an optical detector. Therefore you have to provide a finding chart produced from an optical image.
Do I need to build my OBs such that the execution times in the three arms are identical, in order to be sure the telescope offset is applied only when all exposures are completed?Answer:No. The telescope offset is applied only once the longest exposure series is completed.
- Answer:No, this is not possible. In X-Shooter the offset applies rigidly and simultaneously to all arms.
- Answer:No, this is not possible. Only 1x1 read-out is offered.
Is it useful to attach arc exposures to night time science observations to improve the wavelength calibration accuracy?Answer:This probably makes sense only in the UVB arm, where there are very few night sky lines. For the VIS and especially NIR ar the number of night sky lines is sufficient to guarantee a good refinement of the wavelength solution achieved with the day-time arcs.
- Answer:In the H band spectra a background-dominated (sky+diffuse background) between the OH lines for exposures longer than 10 minutes.
- Answer:With the Threshold Limited Readout (TLR), sky line saturation is not an issue. We have exposed 30min without any problem. Saturation is only a problem for very bright targets that would go over 100,000 electrons in less than about 2 seconds. Basically, with the TLR technique, the counts are computed from the count rate, deduced using all the unsaturated readouts. The detector is read-out every 0.6 sec, the counts accumulated and the count rate used to compute the counts one would reach in the exposure time if there were no saturation. This corresponds to having effectively different exposure times for each pixel.
- Answer:You can use a blind offset from a field star. For doing so, you first need to compute the offset that you need to apply to move the telescope from the reference star to your target, and enter it in arcseconds in the OFFSET.RA, OFFSET.DEC fields of the acquisition window in P2PP. It is alway a good attitude to enter the coordinates of the reference star in the Target window rather than those of the scientific target. This will make the centering of the reference star quicker. This is mandatory if the angular distance between the reference star and the target is larger than the field of view of the X-SHOOTER acquisition camera.
Note that if you use a blind offset, you need to indicate and properly label the reference star in the finding chart. If the distance between the two objects is larger than the FOV of the acquisition camera, you need to provide 2 finding charts, one for the target and one for the reference star.
- Answer:The current calibration plan foresees the observation of one Telluric Standard (TS) (chosen in a list maintained by the Observatory) within 0.2 airmasses and within 2 hours from the science observations. The user can specify a range of spectral types for the TS in the README file under the Special Calibrations section.
If there is the need of having a specific TS observed, then the user should provide the required OBs during Phase 2. Of course, if this is the case, the extra time (which will be charged to the user) needs to be included in the Phase 1 proposal request.
- Answer:The Integral Field Unit (IFU) is rectangular. The position angle (PA) specifies the direction of the long side. So, PA=0 means that the IFU will be placed North-South.
- Answer:Yes, this is in principle possible and, as for all other VLT instruments, it requires the approval by the Observatory. The request needs to be sent as a waiver. See this web page for more details.The user must be aware of the fact that the correction for flexure is only made at the start of the exposure and may degrade over time. However, the degredation is acceptable up to about an hour and 15 minutes.
What is the meaning of the SEQ.IFU.WLGT in the template for Integral Field Unit acquisition SHOOT_ifu_acq ?Answer:In IFU mode there is no correction for atmospheric dispersion. The two ADCs that come after the IFU in the light path are set to their OFF position, where they do not disperse light. Therefore, the user has to choose which wavelength will be kept fixed at the centre of the IFU during the observations. This is done through the SEQ.IFU.WLGT parameter. By default, this is set to the middle of the atmospheric dispersion range (470nm), but it can be set to any value within the X-Shooter range. To minimize the losses, we recommend to place the IFU along the parallactic angle. Also, the users should be aware that, at high airmasses, the amplitude of the dispersion is larger than the 4 arcsec long side of the IFU field. Therefore, depending on the particular choice of SEQ.IFU.WLGT, losses can occurr at either edges of the spectral range.
After the acquisition I would like to add several science templates using different slits. Is this possible?Answer:Yes, this is possible. The various slits are placed very accurately on the right position, and hence there is no need for re-aquisition. You can use any slit you wish after the acquisition.
- Answer:For the first periods of X-Shooter operations the pipeline will deliver wavelength calibrated data only. Object extraction, sky subtraction and all further steps will have to be performed by the user by means of external packages, like MIDAS or IRAF.
- Answer:The minimum DIT is 0.665 seconds. This is the time the IRACE controller takes to read-out the full detector. Entering shorter (or even zero) DIT times in the OBs will always produce effective DITs of 0.665 seconds.
I have a target which is very bright in the NIR, but no so much in the optical. Even with the shortest DIT the object is going to cause strong remnants in the NIR arm. How can I solve this problem?Answer:In principle one can set the NIR slit to the "blind" position, which would effectively close the NIR spectrograph entrance. However, this is not offered in Service Mode. If you really need to do this you must apply for Visitor Mode.