MIDI P2PP Tutorial

This tutorial provides a step-by-step example of the preparation of a set of OBs with MIDI, the mid-infrared interferometric instrument for the VLT. The specifics of this tutorial pertain to the preparation of OBs for Period 82. To follow it, you should have a P2PP installation (for P82, version 2.13.x) in your computer and be familiar with the essentials of the use of P2PP. Please refer to the P2PP Web page for detailed installation instructions and the latest P2PP version to be used, and to the P2PP User Manual for a general overview of P2PP and generic instructions on the preparation of Observing Blocks.

1: Goal of the Run
2: Getting Started
3: Your First OB
- 3.1: Define an OB with P2PP
4: Attaching Finding Charts and ReadMe File
5: Defining the Calibrator OB
6: Finishing the preparation and submitting the OBs

1: Goal of the Run

In this tutorial we will prepare an OB that performs the acquisition of a science target with the N11.3 filter and its fringe observation using the prism. The example consists of observing the supergiant alf Ori (RA (2000) = 05 55 10.31, Dec (2000) = +07 24 25.4) with the baseline UT2-UT4 and within the LST range 06h...09h. Following the science OB for alf Ori, we will construct a second OB that defines the observation of a calibrator target for alf Ori.

The sample OBs will illustrate the use of a variety of features of P2PP and illustrate 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 MIDI. If you have prepared OBs for AMBER before, you will see that many aspects regarding interferometric calibrators, the definition of the baseline configuration, and the setting of sidereal time constraints are very similar for MIDI and AMBER.

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2: Getting started

The Phase 2 process begins when you receive an email from the ESO Visiting Astronomers Section telling you that the allocation of time for the coming period has finalized and that you can view the results by logging into the User Portal and clicking on "Check the web letters." Note that the username and password that you need to use for the User Portal are the same as those you will use to prepare your OBs.

You follow the instructions given by ESO and find that time was allocated to your run with MIDI. Therefore, you decide to start preparing your Phase 2 material. First, you collect all the necessary documentation:

The MIDI User Manual
The MIDI Template Manual
The VLT and ESO-MPI 2.2m Service Mode Guidelines
The P2PP Documentation referred to above.
Consult the MIDI service mode specific webpage

and you proceed with the installation of P2PP on your machine if necessary.

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3: Your First OB

You decide to start with the definition of an OB for your science object.

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3.1: Define an OB with P2PP

For the sake of this tutorial, we will hereafter use the following P2PP information:

P2PP ID: 52052
password: tutorial

This is a special account that ESO has set up so that users who do not have their own P2PP login data can still use P2PP and prepare example OBs. You cannot use this account to prepare actual OBs intended to be executed.

After starting P2PP and logging in using the tutorial account, the P2PP 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 P2PP ID, you will get the list of all the runs in which you are PI.

Select the folder corresponding to the MIDI Tutorial run, 60.A-9253(E). 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 MIDI run.

You can now start defining your OBs.

First, click on the New icon on the upper left side of the P2PP main GUI. This creates an entry under the Summaries area. The red dot 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.

Click on the View icon. The View OB window appears:

This is the window where you will define the contents of your OB.

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3.1.1: Filling in the Basic Information

OB Name

First, you define the OB name, where the name of the OB must follow the specific OB naming convention for MIDI: a science target OB must begin with SCI_ and should preferably contain the target name. In case the same target is also observed with another baseline (which implies that your program contains of several subruns) the OB name could also include the subrun letter code. Assuming for this tutorial example that alfa Ori shall indeed be observed at different baselines, the OB name in this tutorial is SCI_alfori-E, because the run ID for our MIDI run is 60.A-9253(E). Hence, type SCI_alfori-E in the Name field.

User Priority

Next, assign this OB a priority. In case your run contains more than one OB (very likely), you can select a priority for this OB from the drop-down User Priority menu.

OD Name

It may be useful in many cases to have an easy way of identifying an Observing Description (OD), like when having observations of a number of targets performed with identical instrument configuration and observation template parameters. The OD Name field in the View OB window allows you to define names for the ODs. The OD name appears in turn in the Summaries area of the P2PP main GUI, thus allowing the identification at a glance of all OBs having ODs with the same name. In this tutorial the observation description will define the use of the prism for the fringe observations (while the grism would be the other option). Thus, we enter the name Fringe_obs_prism in the OD Name field

User Comments

The User Comments field can be used for any special requirements that you want the staff on Paranal to alert to (for example, to request taking an acquisition image), however, in most cases, this information should be part of the ReadMe attached to this OB, or should be included in the Calibration Requirements tab (see below). Since we don't have any special comments for this example, we leave this field blank.

Instrument Comments: name of associated OB of the SCI/CAL pair

The VLTI specific field Name of associated OB of the SCI/CAL pair must be used to insert the name of the calibrator OB or OBs associated with your science OB SCI_alfori-E. Thus, you enter CAL_hd39400-E in this field.

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3.1.2: Defining the acquisition template

The first template that must be part of any science OB is the acquisition template, so let us define it next. In the

Template
Type

list, make sure that the acquisition entry is highlighted. This will list all the acquisition templates available for MIDI in the Template list next to it.

After reading the description of the templates in the MIDI template Manual, you have noticed that the MIDI_starintf_acq template is the only acquisition template available (well, actually it is also the only possible option in the Template list). You thus click on this template in the Template list, and then on the Add button next to it. The window should now look like this:

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Now, you need to decide on the acquisition parameters, and if necessary, modify the default values given in the acquisition template.

The first fields to fill out in the acquisition template are the correlated and uncorrelated infrared (12 micron) fluxes of the target in the fields Correlated magnitude (Jy) and Uncorrelated magnitude (Jy), as well as the H magnitude of the target in the field Magnitude in H-band. The latter is used for the settings of the IRIS laboratory guiding system. Our target, alf Ori, has an IRAS 12 micron flux of 4682 Jy. We expect a visibility amplitude of 0.6 with the chosen baseline. So, the correlated flux for this observation is 0.6*4682 Jy = 2809 Jy. The H magnitude of alf Ori is -4.0. So, we enter:

Correlated magnitude (Jy): 2809.
Magnitude in H-band: -4.0.
Uncorrelated magnitude (Jy): 4682.

The next two parameters of the acquisition template are related to the direction and amplitude of the secondary mirror chopping. If you notice that the default direction of chopping (chop north, i.e. move target north) would result in a position with background emission, you should change the parameter Amplitude of chopping and/or Angle of chopping. In our example, we choose to chop east (i.e. use blank sky to the west of the target), but leave the chopping amplitude at its default value, and therefore enter:

Angle of chopping:90
Amplitude of chopping : 15 (Default value)

Then you have to enter the filter that should be used for acquisition. Because you know that alf Ori shows a strong emission feature at 11.3 micron, while showing strong absorption at 8.7 micron, the default filter, (please note this is just an example and doesn't have to be true for alf Ori at all), you choose from the filter drop-down menu:

Filter: N11.3

Since your science target, alf Ori, is visually sufficiently bright, it can be used for Coude guiding itself. Therefore you choose the following parameters in your acquisition template:

Coude guide star alpha: 0. (Default value)
Coude guide star delta: 0. (Default value)
Coude guiding type: SCIENCE (Default value)
Coude guide star magnitude in V: 0.6

The values for "Coude guide star alpha/delta " are used in cases where the science target is not bright enough to serve for coude guiding and an off-axis guide star within a radius of 1 arcmin is provided. In that case "Coude guiding type:SETUPFILE" is chosen. The parameter "Coude guide star magnitude in V" is set to the V magnitude of the target that is used for Coude guiding, whether it is the target itself or an off-axis guide star.

The next field to fill out in the acquisition template is Science or calibrator, which obviously must be science since this is your science OB.

3.1.3: Inserting Target Information

At the bottom of the view window you find the Target field where to insert your target name and coordinates. Please insert the target name here, which should be the same name as used in the OB naming, in other words, insert Name: alfori. Also, enter the right ascension and declination for alf Ori. If your target exhibits high proper motion, it is very important to enter this information in the proper motion RA and proper motion DEC fields respectively, unless the proper motion is not available. You may check the Hipparcos catalogue for these values. Please remember to insert the proper motion in RA and DEC in units of arcsec/year. For alfa Ori one enters

proper motion RA: 0.0281
proper motion DEC: 0.0101

Furthermore, edit the entry in the Target-tabbed subpanel Class. In our case , choose Supergiant.

The acquisition template including the target information is now complete, and the window should look like this:

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3.1.4: 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 set of constraints, which indicate under which conditions your OB can be executed. You can do this by clicking on the Constraint Set tab and filling the entries under it:

Name:

First, give a descriptive name to the constraint set about to be defined. Since you have decided that this constraint set will be applied to all the fringe observations, you type Fringe_obs_constraints in the Name field.

Sky transparency:

Since we assume that your observations are typical MIDI mid-IR observations and do not need exceptional atmospheric conditions you request Clear conditions in the Sky Transparency entry.

Baseline:

Let's assume that time has been allocated for your programme on the baselines UT2-UT4 and UT2-UT3, but this run here uses the baseline UT2-UT4. You must therefore choose UT2-UT4 from the baseline drop-down menu.

Note that in your Phase 1 proposal you already specified some of these constraints (sky transparency). You must make sure that none of the constraints specified in Phase 2 is more stringent than the corresponding one specified at Phase 1.

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3.1.5: Setting the time intervals

We will assume now that your MIDI observations are part of a larger multi-wavelength project and that the MIDI observations should be carried out simultaneously with some satellite observations that are performed between May 02-12 2008. You can specify this, i.e. the execution of your MIDI OB between May 02-12 2008 under the

Time
Intervals

tab:

Click on the checkbox at the far right next to the first row of the time intervals.
Modify the lower boundary (the left-hand side entry) of the time interval to the specified starting date of your time window, keeping the same format. In the present case, the entry should read 2008-05-02T00:00:00.
In the same way, modify the upper boundary of the time interval to 2008-05-12T00:00:00.

If your observation could be executed in other, non-contiguous time windows, you could define up to five intervals in the same way as described. However, we also like to remark that setting time intervals for an OB, and thus narrowing the possible execution time dates, limits the possibility that your OB will be successfully executed during the observing period (remember that there is a limited number of service mode time windows available during the period).

3.1.6: Setting the Sidereal Time

Under the Sidereal Time tab you can constrain the LST range within which your OB should be executed. In this tutorial you wish to prepare an OB that should be executed between 06h < LST < 09h, hence you do the following:

Click on the checkbox at the far right next to the first row of the sidereal time.
Modify the lower boundary (the left-hand side entry) of the sidereal time range to the specified starting LST of your LST range, keeping the same format. In the present case, the entry should read 06:00.
In the same way, modify the upper boundary of the sidereal time range to 09:00.

In the same way you could define up to 4 more LST slots, as alternative(!) LST ranges, in case the OB cannot be executed during your prefered LST range setting which you defined in the first row. Please note that defining more than one sidereal time ranges in this field does NOT mean that the OB will be executed at all these LST ranges. Rows 2-5 indicate just the alternatives to the LST range specified in the first row.

3.1.7: Setting the Calibration Requirements

The Calibration Requirements field is the place where you should enter any particular needs for calibrating this OB. For example, if you want to observe instead of the regular CAL/SCI pair the sequence of CAL/SCI/CAL, you must insert this information in the Calibration Requirements field. But note, this information on special calibrations should also be provided in the ReadMe file.

In this tutorial example, and probably for most standard MIDI OBs, no special calibration requirements exist, and the field can be left empty.

3.1.8: Defining the Observation Description/Science templates

Once the acquisition and the tabbed items Target, Constraint Set, Time Intervals, Sidereal time, and Calibration Requirements, are completed, the science template(s) can be inserted.

On Template Type, select now science. The existing MIDI science templates will appear. You find in the MIDI template manual that MIDI_starintf_obs_fringe is the appropriate template for our observation and select it. The template will be attached to the grid below next to the acquisition template selected and filled previously. The other template, MIDI_starintf_obs_field, for field interferometry mode, is only offered for visitor mode observations.

Six parameters have to be defined in the template MIDI_starintf_obs_fringe, which are the Number of frames per photometry exposure, the Fringe tracking at zero OPD, Angle of chopping, Amplitude of chopping, Dispersive element, and the Beam Combiner parameters. In this tutorial we choose the recommeded Fringe tracking at zero OPD=True fringe tracking mode, and PRISM as Dispersive element. Since your target is very bright (in correlated and uncorrelated flux) it is sufficient to obtain 2000 frames per photometry exposure, which is actually the minimum value. If your target would be much fainter it would be advisable to select 4000 or 6000 frames per photometry exposure. The brightness of the target also allows you to use the SCI_PHOT mode, which provides better accuracies on the fringe measurements, and hence, you chose SCI_PHOT as Beam Combiner from the drop-down menu. Finally, you define the same chopping parameters as you had defined in the acquisition template, namely:

Angle of chopping:90
Amplitude of chopping : 15 (Default value)

Now, you are almost done. The only other thing that you should really do at this point is to check the execution time for this OB. The fact that the displayed time does not yet reflect the execution time of the currently written OB is indicated by the small * next to the Execution Time label.

On the top right of the window, below the Add, Delete, and Duplicate buttons you will find a button labeled Recalc ExecTime. Clicking on that button has two effects. First, the small * next to the Execution Time label disappears, and second the calculated OB execution time appears in the display to the right of the label. In this case the total execution time is 00:30:00.

This (almost) completes your first OB! If you followed all the indications given so far, the View OB window should look like this now.

You can now close the View OB window by selecting File -> Close from the top menu bar and you are left with the P2PP main GUI. In there, you should see an entry under Summaries with the following contents:

Name: SCI_alfori-E
Dbaseid: 0
Status: (P)artiallyDefined
Target: alfori
OD: Fringe_obs_prism
CS: Fringe_obs_constraints
Acquisition: MIDI_starintf_acq
FindingCharts: (0)

You can resize the columns as indicated in the P2PP User Manual to view the full contents of each entry.

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4: Attaching Finding Charts and ReadMe File

The next thing to do is to attach the respective Finding Chart(s) to the OB. The Finding Charts must be prepared as jpeg-files and must fulfill all general requirements for finding charts, as well as follow the specific instructions for MIDI Finding Charts outlined on the MIDI service mode specific webpage. You can use any tool of your choice to create the Finding Charts in jpeg-format. P2PP, however, does not contain such an option.

Let's assume you have prepared a jpeg-Finding Chart for this tutorial run [remember: run ID 60.A-9253(E)], which you called 60.A-9253E.alfori01.jpg, and which is saved in a folder of your home directory.

Now, in the P2PP main GUI click on the OB which you want to associate with this finding chart, then select Finding Charts from the top menu bar, which opens a drop-down menu:

From the drop-down menu select Attach Finding Charts, which will open up a new window that allows you to enter path and filename of the Finding Chart you wish to attach to the selected OB. In our example you choose 60.A-9253E.alfori01.jpg and finally click on the Attach Finding Charts button (you could select more than one Finding Chart). The pop-up window will close and the Summaries area of the P2PP main GUI will show the entry

FindingCharts: (1) 60.A-92..

If you are interested in a more comprehensive explanation on how to create and attach or detach finding charts, you should have a look at this page.

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5: Defining the Calibrator OB

Since each science OB must be followed by a calibration OB we will briefly demonstrate how to define the calibrator OB. The necessary steps are very similar to the definition of the science OB.

To select for each science target a calibration target, it is recommended to use the CalVin tool developed by ESO. CalVin selects suitable calibrators based on different user criteria. Optimally you would wish to have a calibrator star as close as possible to and of similar brightness as your science target. Consulting the CalVin tool you find that the star HD39400 is a suitable calibrator for your science target alf Ori.

You repeat the steps as outlined above, i.e. you start defining your calibrator OB by clicking on the New icon on the upper left side of the P2PP main GUI. You fill in the information in the OB view window like you did for alf Ori, now just adapted to the calibrator star HD39400.

Next, as there is just one acquisition template you choose MIDI_starintf_acq. In the case of HD39400 we assume that the chopping default values are fine, and we do not need to modify any parameters in the acquisition template, except for the fields Filter, Coude guide star magnitude in V, and Science or calibrator, as well as Uncorrelated flux at 12 um and Correlated flux at 12 um. In this tutorial we define the same filter for the calibrator acquisition that we chose for the science target acquisition, enter the V magnitude of HD39400, V=4.8, the uncorrelated 12um IRAS flux of 10.7 Jy, the correlated flux of 10.5 Jy (with an expected visibility amplitude of 0.98), and have to set the Science or calibrator field obviously to CALIB. You therefore enter:

Filter: N11.3
Coude guide star magnitude in V: 4.8
Science or calibrator: CALIB
Uncorrelated magnitude (Jy): 10.7
Correlated magnitude (Jy): 10.5

Please note that also the calibrator OB must specify a certain LST range, which is set under the Sidereal Time tab. In particular, the LST range of the calibrator OB must reach from 30 minutes before the start of the LST range of the associated science OB to 30 minutes after the end of the LST range of the science OB. Consequently, the LST range for your calibrator OB is [05:30,09:30]. If such a range cannot be covered with a single calibrator, you can specify (i.e. create another calibrator OB) another calibrator so that the combined LST range meets the above requirement. Please note this in the README file, including any preferences for the calibrators. It is also important at this stage to check that the calibrator is accessible and visible at all times during the specified LST range. Next, you define the parameters of the actual observation template, which is of course the same as selected for the science OB: MIDI_starintf_obs_fringe. It should specify (almost) the same elements as you have defined for the associated science OB, so therefore please choose True, PRISM and SCI_PHOT from the three drop-down menus, respectively. The chopping parameters, however, shall be the same as specified in the acquisition template, where you left the parameters at the default values. So, you don't touch the chopping parameters for this tutorial calibration OB. Concerning the number of frames for the photometry exposure you specify 4000 frames, because the calibrator is significantly fainter and more photometry frames are needed to achieve a similar quality on the calibrator as for the science observation. Finally, your OB view window should look like this:

You close the OB view window and perform the final step, which is attaching a Finding Chart to your calibrator OB. The name of the Finding Chart that you have created is 60.A-9253E.hd39400.jpg. This completes your calibrator OB!

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6: Finishing the preparation and submitting the OBs

With the completion of the OBs, we consider the example developed in this tutorial to be finished. The P2PP main GUI displays the two OBs that we have prepared:

We will now submit these OBs to the ESO Database: select all of them in the Summaries list, go to the File menu in the P2PP main GUI, and select the Check-in option. A dialog box will appear asking for confirmation and, if you click on OK, they will be saved in the ESO Database.

Our tutorial with this example of creating and submitting the OBs for one science target/calibration star pair ends here. For the preparation of the Phase 2 material for a whole run, more OBs may have to be created. Furthermore, the complete Phase 2 material includes also the README file. As of P75, the README file is submitted along with the OBs by using the p2pp tool. A tutorial for the README file is available here . When all the OBs and the README file for a given run are submitted, the Phase 2 submission is finalized by pressing the p2pp-submit button.

As a courtesy to the next user who follows this tutorial, we would like to ask you to finish these exercises by removing the OBs form the ESO Database. By the way, the same procedure would have to be followed should you need to modify your OBs after checking them in, because this action will also lock them. 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-9253(E) in the Prog ID selection criterion
Click on the Query button on the lower left
Select all the OBs that appear 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 afterward you will see them as well.
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.