HAWK-I P2PP Tutorial

This tutorial provides a step-by-step example of the preparation of a set of OBs with HAWK-I, the high acuity wide-field near-infrared imaging instrument for the VLT. To follow the tutorial, you should have a P2PP installation (for P81, version 2.13) on 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.

0: Goal of the Run
1: Getting Started
2: Your First OB

2.1: Define an OB with P2PP

2.1.1: Filling in the Basic Information
2.1.2: Defining the acquisition template
2.1.3: Inserting Target Information
2.1.4: Setting the Constraint Set
2.1.5: Setting the time intervals
2.1.6: Setting the Calibration Requirements
2.1.7: Defining the Observation Description

3: Attaching Finding Charts and ReadMe File
4: Finishing the preparation and submitting the OBs

0: Goal of the Run

In this tutorial we will prepare an OB that performs an imaging observation of a dense stellar cluster in the JHKs filters. Your goal is to obtain precise photometry for the stars in the cluster. The example cluster is called ESO-1, which has a spatial extent of ~5arcmin and whose approximate center is at RA(2000) = 03 15 00.31, DEC(2000) = -07 24 25.4 (Note: This is a fictional stellar cluster).

The sample OB 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 of an observing run, as well as some aspects that are specific to the preparation of OBs for HAWK-I. If you have prepared OBs for ISAAC before, you will see that many aspects are very similar for HAWK-I and ISAAC OBs.

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1: Getting started

The Phase 2 process begins when you receive an email from the ESO Visiting Astronomers Section (Visas) telling you that the allocation of time for the coming observing 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 HAWK-I. Therefore, you decide to start preparing your Phase 2 material. First, you collect all the necessary documentation:

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

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

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2: Your First OB

Now, you start with the definition of an OB for your science target.

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2.1: 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 HAWK-I Tutorial run, 60.A-9253(L). 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 HAWK-I 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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2.1.1: Filling in the Basic Information

OB Name

First, you define the OB name. But since in some special cases a particular prefix must be given to an observing OB, you check first on the Service Mode Guidelines webpage if a special naming convention must be given to your HAWK-I imaging OB. Consulting that page you confirm that your observations do not need any particular OB naming prefix, because it is neither a target-of-opportunity object, nor moving asteroid, nor anything else that would require a particular OB naming prefix. Hence, you decide to name your OB: ESO-1-JHK and you type ESO-1-JHK in the Name field.

User Priority

Next, assign this OB a priority. In case your run contains of 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 OD, like when having observations of a number of targets performed with an 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 imaging observations at J, H, and Ks-band filter. Thus, we enter the name JHKimaging in the OD Name field

User Comments

The User Comments field can be used for any information you wish (to keep further track of the characteristics of the OB, to alert the staff on Paranal to special requirements, etc.). Here, we do not have any special information or requirements and leave this field blank.

Instrument Comments: Magnitude of the brightest object in the field

The HAWK-I specific field Magnitude of the brightest object in the field must be used to insert the J, H, and K-magnitude of the brightest star present in the 7.5arcmin x 7.5arcmin HAWK-I field. In order to retrieve this information you query the 2MASS catalogue. When querying the catalogue you do not provide a search box size of 7.5 x 7.5 arcmin only, but an even larger size of 8 x 8 arcmin to account for the fact that you will define (see below) also a jitter box width of 60arcsec in your science template. The query result tells you that the brightest object in the whole field has the magnitudes: J=11.2, H=11.0, K=10.7mag. You verify on the HAWK-I service mode specific webpage that this is not too bright for HAWK-I observations (Note: imaging observations leading to strong detector saturation are not schedulded in service mode) and you continue with typing J=11.2 H=11.0 K=10.7 into the Instrument Comments field

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2.1.2: 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 HAWK-I in the Template list next to it.

After reading the description of the templates in the HAWK-I template Manual, you have noticed that the HAWKI_img_acq_Preset template is the acquisition template most suited for your purpose, because a very precise target centering is not neccessary. Therefore you click on the template named HAWKI_img_acq_Preset from the list of possible templates in the Template list. Then, you click 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 DIT (detector integration time for a single read) and NDIT (number of DITs to co-average) settings. Your decision for the values of DIT and NDIT depends on the brightness of the target. Since your stellar cluster contains bright stars and is easily identifiable in a short exposure of 10seconds at J-band, you enter:

DIT (secs): 10
NDIT: 1

The next three parameters of the acquisition template are related to the orientation and positioning of the field before the first imaging exposure is taken. In our tutorial example we assume that a very interesting object is present very close to the cluster center. This object would fall into the gap between the HAWK-I detectors during the acquisition. In order to prevent this the parameters Offsets in Alpha and Offsets in Delta are given a value, so that the telescope executes an offset before starting to take the images. In our example, we choose to offset 15arcsec in RA and 15arcsec in DEC. The rotation of the field, which is defined by the parameter Position Angle on Sky (deg), is not important for us as the cluster is quite symetric, and you decide to keep the default value of 0deg. So, you enter:

Offsets in Alpha: 15
Offsets in Delta: 15
Position Angle on Sky (deg): 0 (Default value)

Next, you have to decide about the telescope guide star. It may happen that one wants to observe a region in a large dark cloud where no optically bright star is present that can be used for the telescope active optics guiding. In such a case the parameter Telescope Guide star selection must be set to NONE. However, in the large majority of cases, and also in our tutorial example, it is no problem for the telescope operator to automatically find a telescope guide star from the catalogue. Therefore, in most cases and so for our example here this field can be left at it's default value:

Telescope Guide Star Selection: CATALOGUE (Default)

Only in case the Telescope Guide star selection is set to SETUPFILE are the values for "RA/DEC of telescope guide star", the next acquisition template keywords, used.

Finally, you have to enter the filter that should be used for acquisition. It is recommendable to chose the same filter as you will use in your first science template, and because you decide that this will be J-band, you choose from the filter drop-down menu:

Filter Name: J

2.1.3: Inserting Target Information

At the bottom of the view window you find the Target field where your target name and coordinates are to be inserted. Here please insert the target name, which could be the same name as used for the OB itself. In other words, insert Name: ESO-1. Also, enter the right ascension and declination for ESO-1.

Right Ascension: 03:15:00.31
Declination: -07:24:25.4

Furthermore, edit the entry in the Target-tabbed subpanel Class. In our case , choose OpCl for Open Cluster. All other Target related fields can be left at their default values.

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

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2.1.4: 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 JHK imaging observations, you type JHK_constraints in the Name field.

Sky transparency: Since you wish to be able to determine accurate fluxes from your images, you request Photometric conditions in the Sky Transparency entry.

Seeing: Since you need moderately good quality in your images, you specify 0.8 as the value of the Seeing field.

Airmass: Set the Airmass to 2.0, to ensure that your observations are not carried out at too low an elevation.

Lunar illumination and Moon Angular Distance: Since you are doing broad band observations in the near-infrared, the lunar illumination has very little influence. You can thus leave the default values of 1.0 and 30 degrees for the Lunar Illumination and Moon Angular Distance fields.

NOTE: In your Phase 1 proposal you already specified some of these constraints (lunar phase, seeing, and transparency). At Phase 2, you can relax your constraints to improve the chances of execution of your programme, but you cannot specify more stringent constraints.

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2.1.5: Setting the time intervals

We will assume now that your HAWK-I observations are part of a larger multi-wavelength project and that the HAWK-I observations should be carried out simultaneously with some satelite observations that are performed between September 02-12 2008. You can specify this, i.e. the execution of your HAWK-I OB between September 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 2008-09-02T00:00:00.
In the same way, modify the upper boundary of the time interval to 2008-09-12T00:00:00.

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 wish 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 are only limited service mode time windows over the period).

2.1.6: Setting the calibration requirements

The Calibration Requirements field are free text fields where you should enter any particular needs for calibrating this OB. If this is lengthy or complicated, add a reference to the README file, where you should explain it in detail. We will leave it blank in this example.

2.1.7: Defining the Observation Description/Science templates

Once the acquisition and the tabbed items Target, Constraint Set, Time Intervals, and Calibration Requirements, are completed, the science template(s) can be inserted. In this example OB, we will insert three science templates (one after the other), as we wish to define an observing sequence of exposures with the J, H and Ks filters.

On Template Type, select now science. The existing HAWK-I science templates will appear.

Now, you have to make a choice between the different HAWK-I imaging templates which is driven by the scientific requirements of your programme and the specialities of your target. Since the stellar cluster we are considering in this tutorial example is large in extent and very rich, it will be impossible to obtain a good estimate of the sky background. A good strategy will be to obtain separate sky offset fields far away from the cluster. You consult the Template Reference manual and you select the template HAWKI_img_obs_FixedSkyOffset from the template list. Click on the Add button to attach the template to the grid below next to the acquisition template selected and filled previously.

The OB view window should look like this now:

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In order to fill out all parameters of this observing template you consider the following: using the information provided by a near-infrared survey (e.g. 2MASS) you find out that a sky field 510 arcseconds East and 340 arcsecs South of your cluster has a relatively low stellar density and does not contain any bright stars. Hence, this field is perfectly suited as a sky field. Further, you want to apply a random jitter pattern within a 60 arcsec box on your object and your sky fields. You also want the brightest source in your field not to saturate heavily (no more than a factor 5 above saturation level), but still want to obtain a sufficient signal to detect fainter sources. After consultation of the manual and the Exposure Time Calculator you find that you will approximately need a total on-source time of 480s per filter, and that the recommended DITs for JHKs are 10s. In addition, you recognize the rule that the minimum time spent at a jitter position (=DIT * NDIT) is 60s. You decide to set DIT to 10s and NDIT to 12 for the J band. The final strategic consideration concerns the sky fields: you see that more than 3 ABcycles should be obtained to be able to construct a median sky. So, you decide to define 4 ABcycles, this results in 4 jitter positions on the sky and on the object, respectively, a reasonable number (it should not be much lower). For the sky fields you wish to spend only half of the observing time, and hence you set NDIT to 6 for the sky. Furthermore, you decide to start the jitter in each filter at the reference position given by the acquisition, rather than at the last position observed in the previous template. The first HAWKI_img_obs_FixedSkyOffset template (the observation in J) thus has the following parameters:

DIT (secs): 10
Number of exposures per offset: 1
Return to Origin ? (T/F): checked (i.e., True) (the telescope will thus return to the initial position after the execution of the template)
Jitter Box Width (arcsec): 60
Number of AB or BA cycles: 4
NDIT on OBJECT positions: 12
NDIT on SKY positions: 6
Type of first observation: O (Default)
Alpha Offset (arcsec): 510
Delta Offset (arcsec): -340
Filter Name: J

... and the template section in your OB window should look like this now:

For H and Ks band, you rather want to set the DIT to 5s, NDIT to 24, and again only half that much for the sky, hence NDIT to 12 for the sky fields.

For the observations in H and Ks, you could select again the same template, Add it, and fill the parameters in the same way as done for the template in J. However, since the parameters of these other two templates will be very similar to those of the one just defined, you can speed up the preparation by clicking on any entry of the template for the J-band observation, then clicking on the Duplicate Col button on the upper right. In this way, you will have produced an identical copy of the first science template in which you should now only edit the parameters that change from template to template:

DIT (secs): 10 must be changed to 5
NDIT on OBJECT positions: 12 must be changed to 24
NDIT on SKY positions: 6 must be changed to 12
Filter Name: J must be changed to H

In a similar manner, you create your Ks-band observing template by duplicating the H-band template and modifying the filter entry. However, the only other change in this Ks-band observing template is that you do not check the Return to Origin ? (T/F): box, because offsetting back to the original position is not needed and neglecting this offset will save you OB execution time.

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 01hour 01min 36sec.

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: ESO-1-JHK
Dbaseid: 0
Status: (P)artiallyDefined
Target: ESO-1
OD: JHKimaging
CS: JHK_constraints
Acquisition: HAWKI_img_acq_Preset
FindingCharts: (0)
EphemerisFile:

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

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3: Attaching Finding Charts

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 HAWK-I Finding Charts outlined on the HAWK-I 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(L)], which you called 60.A-9253L.ESO-1.jpg, and which is saved in a sub-directory 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-9253L.ESO-1.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.

4: Finishing the preparation and submitting the OBs

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

We will now submit the OB to the ESO Database: select it 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 HAWK-I OB for JHK imaging using a fixed sky offset 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. 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(L) 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 submitted OB 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.