X-SHOOTER P2PP Tutorial

This tutorial provides a step-by-step example of the preparation of a set of OBs with XSHOOTER at the ESO-VLT. There is also a Video Tutorial available.

To follow it, you should have a p2pp3 installation in your computer and be familiar with the essentials of the use of p2pp3. Please refer to the P2PP3 Web page for detailed installation instructions, and to the p2pp3 User Manual for a general overview of p2pp3 and generic instructions on the preparation of Observing Blocks.

0: Goal of the Run

In this tutorial we will prepare OBs for a simple example observing run, consisting of spectroscopy of Eta Car (RA(2000) = 10:44:39.1, Dec(2000) = -59:37:44). The sample OBs will illustrate the use of a variety of features of p2pp3 and the kind of decisions to be taken at the time of preparing in advance an observing run, as well as some aspects that are specific to the preparation of OBs for XSHOOTER. In this imaginary observing programme, we wish to observe Eta Car with two perpendicular slit orientations, and the two observations must be taken in immediate succession.

1: Getting Started

The Phase 2 process begins when you receive a communication of the ESO Observing Programmes Office (OPO) communicating to you that the allocation of time for the coming period has finalized and that the results can be consulted in the corresponding Web page. You follow the instructions given by ESO and find that time was allocated to your run with XSHOOTER. Therefore, you decide to start preparing your Phase 2 material. First, you collect all the necessary documentation:

and you proceed with the installation of p2pp3 in your machine if necessary. For the sake of this tutorial, we will hereafter use the following p2pp3 information:

  • p2pp3 ID: 52052
  • password: tutorial

This is a special account that ESO has set up so that users who do not have their own p2pp3 login data can still use p2pp3 and prepare example OBs. You cannot use it to prepare actual OBs intended to be executed. After logging into the tutorial account, the p2pp3 main GUI will appear as follows:

Runs for a number of instruments appear in the Folders area, since the same tutorial account is used for all of them. Similarly, if you log in with your own p2pp3 ID, you will get the list of all the runs in which you are PI.

2: Making OBs

Select the folder corresponding to the XSHOOTER Tutorial run, 60.A-9253(P). In this tutorial we assume that time was allocated in Service Mode. This is indicated by the SM letters that appear next to the Run ID of the XSHOOTER run.

You can now start defining your OBs. Since we want our two OBs to be executed in sequence, we must define them inside a Concatenation. Select the program folder and click on the big purple C icon. Then highlight the Concatenation and press Enter to rename it "eta Car 37.5 and 127.5 deg" as shown:

To create the first OB, click on the dark-blue OB icon. This creates the OB inside the Concatenation. The red dot with an "x" next to the OB name means that the OB fails to pass some fundamental verification criteria, as may be expected from the fact that no template has been attached to the OB yet. It is always a good idea to give meaningful names to OBs, so that you can browse through the list and easily recognize them. In our first example, we will build an OB to take a spectrum of Eta Carinae using XSHOOTER with one of the two required slit position angles; for this reason we will call the OB "etaCar 37.5deg" by renaming it as we did for the concatenation.

Now click on the Edit icon (highlighted in the above figure), and the OB editing window appears. This is the window where you will define the contents of your OB. Alternatively, you can just double click on the OB line in the main p2pp3 window, and the OB will open up in edit mode.

2.1: Defining the acquisition template

An OB is defined in a set of one or more templates that form the Observation Description, or OD for short. It may be useful in many cases to have an easy way of identifying an OD, like when having observations of a number of targets performed with identical instrument configuration and exposure times. The OD Name field in the OB window allows you to define names for the ODs. The OD name appears in turn in one of the columns of the p2pp main GUI, thus allowing the identification at a glance of all OBs having ODs with the same name.

In this example OB, the OD will consist of a a single spectrum of eta Car at a specific position angle. We can thus appropriately name it eta Car 37.5 deg. We enter this name in the OD Name field.

The first template that must be part of any OB that requires a definite pointing is the acquisition template, so let us define it first. In the Template Type pull-down menu, make sure that the acquisition entry is highlighted. This will list all the acquisition templates available for XSHOOTER in the Template list under it.

After reading the description of the templates in the XSHOOTER User Manual, you have determined that the XSHOOTER_slt_acq is the acquisition template you have to use for this particular observation. You thus click on this template in the Template list, and then on the Add button next to it.

You need to decide now on the acquisition parameters. Since we want to acquire directly on Eta Carinae, we will set RA and DEC blind offsets to 0. Moreover, the target has no meaningful proper motion and therefore you do not need any additional tracking velocity. You also do not have any special requirements on the guiding star, which will be selected in the VLT guide star catalogue and hence there is no need to specify any coordinates for the guiding star.
Since you want to place the slit on a position angle of 37.5 degrees, you have to specify ththis number in the Position Angle on Sky field.
The set of parameters that you choose in your acquisiton template is shown in the previous figure.

In case you want to acquire a faint target (V>22.5mag) you have to do a blind offset. That means you specify the coordinates of a reference object in the target field (see below), and specify the offset RA and offset Dec of your science target to that refernce target in the respective fields of the acquisition template.

2.2: Setting the target information

By default, the OB editor opens in the "Obs. Description" mode. To enter information on the target, click the "Target" icon at the top of the window.In the Name field, type the target name "eta Car"). In the Right Ascension, Declination fields, type the coordinates. Since the coordinates are given for both epoch and equinox J2000, leave these fields with their default values. You can give also the Class to which this object belongs, for archival purposes. In this case, choose Pec* (peculiar star).The proper motion of this target is negligible for the purposes of this example, and differential tracking of the telescope is not needed since this is not a moving Solar System target. Therefore, you can leave the last four fields in the Target tab set to their default values of zero.

In case you need to do a blind offset (for targets with V>22.5mag), you have to specify the reference star coordinates in the Right Ascension, Declination fields.

2.3: Setting the constraint set

As stated in Section 1, we assume for the purposes of this tutorial that the program has been allocated time in Service Mode. You thus need to specify a constraint set for your OBs. You can do this by clicking on the "Constraint Set" icon and filling the entries under it:

First, give a descriptive name to the constraint set about to be defined. In this case we choose "eta Car Photometric" for the Name field. In the Sky Transparency entry we choose "Photometric", and since you need moderately good quality in your images, you specify 1.0 as the value of the Seeing field. Set the Airmass to 2.0, to ensure that your observations are not carried out at too low an elevation. Since you are doing spectroscopy of a bright target, the lunar illumination has very little influence, so you decide to leave the lunar parameters at their default valules.

Note that in your Phase 1 proposal you already specified some of these constraints (lunar illumination, seeing, transparency). You must make sure that none of the constraints specified in Phase 2 (i.e., in your OBs) is more stringent than the corresponding one specified at Phase 1 (Phase 2 constraints must agree with Phase 1 request).

2.4: Setting time intervals

We will assume now that the spectroscopy of Eta Carinae has to be obtained in Jan 2013, since you will have simultaneous observations at other wavelengths during that time interval. You can specify this by clicking the Time Intervals icon. You are now asked to "Click the New TI button to add a Time Interval". Now the following window pops up and you can adjust the time interval:

When clicking OK, the time interval is entered into the OB (see picture below). If your observation could be executed in other, non-contiguous time windows, you can define multiple intervals in the same way as described.

Note that such time critical aspects must also be explained in the section on "Time Critical Aspects" of the Readme. It is not sufficient to enter the constraints only here.

For more information on entering time constraints and how to use Time Link containers to enter relative time constraints, see the description in the p2pp3 manual.

2.5: Defining the Observation

Once the acquisition is completed, the science observation begins, so the observing templates need to be attached. After checking with the manual and considering the scientific requirements of your program, you have found that the suitable template to be used is XSHOOTER_slt_obs_GenericOffset.

On Template Type, select now science. The existing XSHOOTER science templates will appear. Select the chosen one, XSHOOTER_slt_obs_GenericOffset, and click on Add. The template will be attached to the grid below next to the acquisition template selected and filled previously. What you need to do next is to set the parameters in the science template.

Following the recommendations of the manual, you choose to use the standard read-out mode 100k/1pt/hg. For your scientific purposes you need to obtain spectra of 100 seconds in the UVB of Eta Carinae, which is definitely an extended object. Therefore you decide not to nod on the slit, but to take separate sky exposures. You adjust the slit widths for the different arms to the requested seeing (this will be slightly better in the NIR). Note that the UVB and VIS arm share the same FIERA controller and thus cannot be read-out simultaneously. In order to optimise your science time, you can add the time needed to read-out the UVB arm (68s) , as exposure time to the VIS. The NIR arm can be read-out simultaneously, and has a very short read-out time (1.44s). Take a look at the user manual (p50) if you want to optimise your exposure times and minimise overheads. The set of parameters that you choose in your science template is thus as depicted below:

You can now compute the execution time clicking on the Recalculate button next to the Execution Time field.

NOTE: after each modification in the OB, the execution time field is not updated automatically, and you need to click on the Recalculate button to display the correct value.

Finally, to complete the OB preparation, enter the expected signal-to-noise ratio and the preferred spectral type for the telluric standard star in the Instrument Comments field, using the following syntax: S/N=XYZ @ xyz nm; preferred telluric: xx-star

This completes your first OB! If you followed all the indications given so far, the OB window should look like the image above.

2.6: Attaching Finding Charts and the README file

Finding charts and README file are directly attached to the OBs. Please, see the respective tutorials on Finding Charts and README for instructions on how to do that.

2.7: Making more OBs

We want to add one more OB to our Concatenation in order to take a spectrum with the slit direction perpendicular to that of the first OB. Since most of the OB parameters will be identical, the easiest is to duplicate the OB we've already made. In the main p2pp3 GUI window, select the OB and click the Duplicate button. See picture:

This will add an identical OB to the concatenation. We rename this new OB to "eta Car 127.5deg". Clicking the Edit icon, we now only need to change two things: (1) the value of the Position Angle in the acquisition as shown in the image below, and (2) attach a different finding chart showing the proper slit position.

3: Finishing the preparation and submitting the OBs

With the completion of the OBs above, we consider this tutorial terminated. As already mentioned, it has certainly not covered all the observing strategies you may have foreseen for your program, but it has shown how to prepare OBs for a representative case.

The p2pp3 main GUI now displays the two OBs that we have prepared:

Note that the red cross has been replaced with a check mark, indicating that the OB new passes some fundamental tests. However, we still need to Verify the OB before submitting them to ESO. To do this, highlight the OBs and select the menu item Reports > Verify. This step runs a Verification Module checking that the structure and all the parameters we have specified are compliant with the instrument specifications. Please note that should you obtain error messages (compared to only warnings), you will not be able to Check-In your OBs to the ESO Database before having solved the errors.

We will now submit these OBs to the ESO Database. Select all of them again, select File > Check-in from the menu in the p2pp main GUI. A dialog box will appear asking for confirmation and, if you click on OK, they will be saved in the ESO Database. Once this is done, the ingested OBs will be locked and no further modification is possible, unless you first check them out. This status is indicated by a lock symbol.

4: Check-Out and removal of tutorial OBs from the ESO Database

As a courtesy to the next user who follows this tutorial, we would like to ask you to finish these exercises by checking-out and removing the OBs form the ESO Database. The p2pp User Manual gives you detailed indications on how to do this. In short,

  • Select Check-out... from the File menu in p2pp
  • In the Database Browser window that opens, type 60.A-9252(G) in the Prog ID selection criterion
  • Select other keywords you may want to be displayed (e.g. Target, Instrument and so on)
  • Click on the Query button on the lower left
  • Select the OBs you have created in the display area after the query. Normally there should be your two submitted OBs only, but if another user has submitted other OBs from this same account without removing them afterwards you will see them as well (as in the following example).
  • Under the File menu in the View OB window, select Check-out

In this way the OBs will be removed from the ESO Database and will be left in your Local Cache only. From there you can delete them if you like by selecting them and choosing the Delete option under the File menu in the p2pp main GUI.

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