VISIR P2PP Tutorial

This tutorial provides a step-by-step example of the preparation of a set of Observing Blocks (OBs) with VISIR, the VLT spectrometer and imager for the mid-infrared. The specifics of this tutorial pertain to the preparation of OBs from Period 90 onwards. To follow the tutorial, you should have a P2PP installation on your computer and be familiar with the essentials of the use of P2PP. Please refer to the P2PP Webpages for detailed installation instructions, 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

In this tutorial we will prepare two OBs, one imaging OB and one spectroscopic OB. In both cases the target is a young stellar object named He3-298 possessing a circumstellar disk. We assume that you wish to image He3-298 with a PAH filter at 11.25 micron and observe it spectroscopically at low resolution. The target has the following coordinates: RA(2000) = 09 36 44.4, Dec(2000) = -53 28 00. We will start with the construction of the imaging OB, followed by a long-slit spectroscopy OB.

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 VISIR.

1: Getting started

The Phase 2 process begins when you receive an email from the ESO Observing Programmes Office (OPO) informing you that the allocation of time for the coming period has been 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 login to the User Portal are the same as those you will need to provide to P2PP.

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

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

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2: Your first OB- Starting 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 VISIR tutorial run, 60.A-9253(I). In this tutorial we assume that time was allocated in Service Mode. This is indicated by the SM letters that appear next to the RunID of the VISIR run.

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2.1: Define an imaging OB with P2PP

Once you have selected the VISIR folder in the Folders area, you can start defining your first OB.

First, click on the OB icon on the upper left side of the P2PP main GUI. This creates a new OB in the selected folder. You may now change the name of the newly created OB. Preferably, you like to be able to identify later that this OB is associated with the target He3-298 and that it is an imaging OB. Therefore, you choose the OB name He3-298-ima. Click on the OB, and press enter, then type this name He3-298-ima.

Now click on the Edit Observing Block 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

 

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 theP2PP main GUI, thus allowing the identification at a glance of all OBs having ODs with the same name. In this tutorial OB the observation description will define the use of the PAH2 filter at 11.25 micron. Thus, we enter the name Imaging_PAH2 in the OD Name field.

User Comments

The User Comments field can be used for any information you think is important for the night astronomer at the time the OB is executed, e.g. to keep further track of the characteristics of the OB, to alert the staff on Paranal to special requirements (but also see the reference below to the Calibration Requirements 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 VISIR in the Template list next to it.

After reading the description of the templates in the User Manual, you have noticed that the VISIR_ima_acq_MoveToPixel template is your choice, because you are using the intermediate pixel scale (pfov 0.076 arcsec) and you want to make sure that your target gets very well centered. 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:

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

There are three parameters related to the telescope nodding and the secondary mirror chopping. Since your target is relatively little extended (less than 4 arcseconds in diameter) and also an isolated source, you decide to chop on the array, without changing the default chopping position angle. Furthermore, since you will choose a perpendicular relative chop/nod direction in your later science observations, you also select a perpendicular relative chop/nod direction for the acquisition. Thus, you enter the parameters (or select from the drop-down menu):

  • Relative Chop/Nod Direction: PERPENDICULAR
  • Chopping Position Angle: 0 (Default value)
  • Chopping Amplitude: 10

The next parameter to enter is the total integration time that will be necessary to clearly identify your target. Since He3-298 is bright, the minimum of 30 seconds is sufficient for that purpose. Hence, you enter

  • Total integration time: 30.0

You will also have to make a choice on the filter used during the acquisition, which should, in general, be selected in such a way that a high signal to noise on the target is achieved in relatively short time. In our tutorial example the continuum filter next to the PAH2 filter is the right choice. Furthermore, you wish to use the finest pixel scale. Therefore, you select from the drop-down menus:

  • Imager filter: PAH2_2
  • Imager pixel scale: 0.076

For the rest of the parameters in the acquisition template you can leave the default value.

 

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2.1.3: Inserting Target Information

Now press the Target button at the top of the edit window. The target edit window appears with fields where to insert your target name and coordinates. Here please insert the target name, which can be (for easy cross-identification purposes) the same name as used in the OB naming, in other words, insert Name: Hen 3-298. Also, enter the right ascension and declination for He3-298.Furthermore, edit the entry in the Target-tabbed subpanel Class. In our case, choose YSO (Young Stellar Object).

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 icon at the top of the edit window 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 imaging OBs of this target, you type He3-298-imaCons in the Name field.

Sky transparency:

Since we assume that your imaging observations aim at constraining as accurate as possible the mid-infrared luminosity of He3-298 and itscircumstellar disk, you need very good atmospheric conditions. You request Photometric conditions in the Sky Transparency entry.

Seeing:

As for the seeing constraint, you know that the image quality at 10 microns is diffraction-limited if the optical seeing is better than ~0.8 arcsec, and since spatial resolution is a key issue for your study, you enter 0.8 in the Seeing field.

Airmass:

The airmass is not a stringent parameter for the imaging part of your programme, you thus enter 2.0 in the Airmass field.

Lunar Illumination and Moon Angular Distance

The moon has essentially no effect at all on the VISIR data quality, and constraints related to the moon are not considered for OB qualification. The default values are hence simply accepted.

Twilight Constraint:

Since the solar position has little effect on the sky brightness in the mid-infrared, you are Ok with your observations being doing in twilight. Therefore you enter -60 in the Twilight field to allow your observations to be started a maximum of 60 minutes before the start of astronomical twilight.

PWV:

As you are doing imaging observations in the N-band, PWV is only moderately important for your science goals, so you request your observations to be done under PWV conditions of 3 mm or less. Therefore you enter 3.0 conditions in the PWV field.

Note that in your Phase 1 proposal you already specified some of these constraints (sky transparency, seeing). 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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2.1.5: Setting the time intervals

We will assume now that your VISIR observations are part of a larger multi-wavelength project and that the VISIR observations should be carried out simultaneously with some satelite observations that are performed between October 01-31 2012. You can specify this, i.e. the execution of your VISIR OB between October 01 and October 31, 2012 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 2012-10-01T00:00:00.
  • In the same way, modify the upper boundary of the time interval to 2012-10-31T00:00:00.

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.

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2.1.6: Defining the Observation Description

Once the acquisition and the items TargetConstraint Set, and Time Intervals are completed, the science template(s) can be inserted. Click on Obs. Desciption to view the observation description.

On Template Type, select now science. The existing VISIR science templates will appear. Select the template VISIR_img_obs_AutoChopNod and click on Add. The template will be attached to the grid below next to the acquisition template selected and filled previously.

Several parameters have to be defined for this template. In the following we discuss each of them and justify a certain choice based on the properties of the target He3-298 and the scienctific goal of this imaging OB. First, you have to decide if you prefer to nod perpendicular or parallel to the direction of the chop. From the manual you extract that for not very extended sources and observations that aim at high spatial resolution, the perpendicular relative chop/nod is recommended. From the pull-down menu you therefore select:

  • Relative Chop/Nod Direction: PERPENDICULAR

Several bad pixels or cosmics will produce an errornous response at some parts of the array. Therefore you want to avoid the target's signal falling permanently on a bad pixel and you choose to jitter on the nod positions by setting:

  • Random Jitter Box Width: 3

After using the exposure time calculator for VISIR in imaging mode, you know that 600 sec of total integration time is needed on He3-298in order to reach the signal to noise ratio you want. Thus,

  • Total integration time: 600

The next two parameters, again, are related to chopping and we will make the same selection as in the acquisition template, because the same rules apply here:

  • Chopping Position Angle: 0 (default)
  • Chopping Amplitude: 10

Then, you have to select the imaging filter for this observation. In principle, you are interested in imaging the PAH feature at 11.25 microns, which implies the filter PAH2. But of course, it is also necessary to perform the same observations with a reference filter, close by in wavelength and centered on the continuum in orderto separate the continuum contribution from the true 11.25 micron emission. Since the continuum reference filter PAH2_2 is already in place (being used for the acquisition), we do the continuum imaging first and select:

  • Imager filter: PAH2_2
  • Imager pixel scale: 0.075

If you followed all the indications given so far, the View OB window should look like this now.

 

The observation that must now follow, and which should be defined within the same OB, is the imaging at the actual PAH filter, PAH2. In other words, you must append another VISIR_img_obs_AutoChopNod template. Select this template from the list of science templates and click on the Add button next to it on the right. Assign to the parameters exactly the same values as you did in the previous VISIR_img_obs_AutoChopNod  template, with the only difference in the imaging filter, for which you select:

  • Imager filter: PAH2

The OB view window should now look like this:

 

The only other thing that you should really do at this point is to check the execution time for this OB. Next to the Execution Time label you will find a button labeled Recalculate. Click on this button to calculate the execution time for your OB.

This (almost) completes your first OB! You can now close the View OB window and you are left with the P2PP main GUI. In there, you should see an entry under Summaries with the following contents:

  • Name: He3-298-ima
  • Status: (P)artiallyDefined
  • Target: He3-298
  • OD: Imaging_PAH2
  • CS: He3-298-ImaCons
  • Acquisition: VISIR_img_obs_MoveToPixel
  • FindingCharts: (0)

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

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2.1.7:Attaching Finding Charts

The last thing to do, which finishes the preparation of a single OB, 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 and VISIR-specific requirements for finding charts. 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(I)], which you called 60.A-9253I.he3-298.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-9253I.he3-298.jpg and finally click on the Attach Finding Charts button (you could select more than oneFinding Chart). The pop-up window will close and the Summariesarea of the P2PP main GUI will show the entry

  • FindingCharts: (1) 60.A-92..

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2.2: Define a spectroscopic OB with P2PP

In the next section of this tutorial, we will define an OB to do long-slit low-resolution spectroscopy on the same target, He3-298.

We start by again clicking on the OB icon on the upper left side of the P2PP main GUI to create a new OB. You may now change the name of the newly created OB. Preferably, you like to be able to identify later that this OB is associated with the target He3-298 and that it is a spectroscopic OB. Therefore, you choose the OB name He3-298-spec. Click on the OB, and press enter, then type this name He3-298-spec.

Now click on the Edit Observing Block icon. The View OB window appears:

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

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2.2.1: Filling in the Basic Information

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 identical instrument configuration and observation template parameters. The OD Name field in the View OB window allows you to define namesfor the ODs. The OD name appears in turn in the Summaries area of theP2PP main GUI, thus allowing the identification at a glance of all OBs having ODs with the same name. In this tutorial OB the observation description will define the use of low-resolution spectroscopy across the N-band. Thus, we enter the name Spectroscopy-N in the OD Name field

User Comments

The User Comments field can be used for any information you think is important for the night astronomer at the time the OB is executed (e.g. to keep further track of the characteristics of the OB, to alert the staff on Paranal to special requirements (but also see the reference below to the Calibration Requirements field)).

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

After reading the description of the templates in the User Manual, you have noticed that the VISIR_spec_acq_MoveToSlit template is your choice, because you are doing spectroscopy of a relatively bright source. 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:

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

There are three parameters related to the telescope nodding and the secondary mirror chopping. Since your target is relatively little extended (less than 4 arcseconds in diameter) and also an isolated source, you decide to chop on the array. However, your source has a companion at a position angle of 64 degrees, which you would like to avoid having in the slit. So you choose a slit rotator angle of 360-154=206 degrees, which is perpendicular to this, and a relatively narrow slit width of 0.4 arcseconds. Furthermore, since you wish to chop within the slit, you choose a long slit, a chopping angle that is identical to the slit rotator angle, and a parallel relative chop/nod direction. Thus, you enter the parameters (or select from the drop-down menu):

  • Relative Chop/Nod Direction: PARALLEL (Default value)
  • Rotator on Sky (=-PA on Sky): 206
  • Chopping Position Angle: 206
  • Chopping Amplitude: 10
  • Spectrometer Slit Type: LONG (Default value)
  • Spectrometer Slit Width: 0.40

The next parameter to enter is the total integration timethat will be necessary to clearly identify your target. Since He3-298 is bright, 60 seconds is sufficient for that purpose.Hence, you enter

  • Total integration time: 60.0

You will also have to make a choice on the filter used during the acquisition, which should, in general, be selected in such a way that a high signal to noise on the target is achieved in relatively short time. Since our target He3-298 has a relatively red energy distribution over the N-band, we choose the long-wavelength broad-band N_LW filter. Therefore, you select from the drop-down menus:

  • Acquisition filter: N_LW

For the rest of the parameters in the acquisition template you can leavethe default value.

 

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2.2.3: Inserting Target Information

Now press the Target button at the top of the edit window. The target edit window appears with fields where to insert your target name and coordinates. Here please insert the target name, which can be (for easy cross-identification purposes) the same name as used in the OB naming, in other words, insert Name: Hen 3-298. Also, enter the right ascension and declination for He3-298.Furthermore, edit the entry in the Target-tabbed subpanel Class. In our case, choose YSO (Young Stellar Object).

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

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2.2.4: 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 yourOB can be executed.You can do this by clicking on the Constraint Set icon 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 imaging OBs of this target, you type He3-298-specConsin the Name field.

Sky transparency:

You wish to obtain your spectroscopic observations of He3-298 in conditions offering good atmospheric transparancy in the direction of your target. You thus request Clear conditions in the Sky Transparency entry.

Seeing:

As for the seeing constraint, you know that the image quality at 10 microns is diffraction-limited if the optical seeing is better than ~0.8 arcsec, and since spatial resolution is a key issue for your study, you enter 0.8 in the Seeing field.

Airmass:

To achieve a good telluric correction, you wish your observations to be done at relatively low airmass. You thus enter 1.6 in the Airmass field.

Lunar Illumination and Moon Angular Distance

The moon has essentially no effect at all on the VISIR data quality, and constraints related to the moon are notconsidered for OB qualification. The default values are hence simply accepted.

Twilight Constraint:

Since the solar position has little effect on the sky brightness in the mid-infrared, you are Ok with your observations being doing in twilight. Therefore you enter -60 in the Twilight field to allow your observations to be started a maximum of 60 minutes before the start of astronomical twilight.

PWV:

As you are doing spectroscopic observations in the N-band, PWV is only moderately important for your science goals, so you request your observations to be done under PWV conditions of 3 mm or less. Therefore you enter 3.0 conditions in the PWV field.

Note that in your Phase 1 proposal you already specified some of these constraints (sky transparency, seeing). 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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2.2.5: Setting the time intervals

We will assume now that your VISIR observations are part of a larger multi-wavelength project and that the VISIR observations should be carried out simultaneously with some satelite observations that are performed between October 01 and October 31, 2012. You can specify this, i.e. the execution of your VISIR OB between October 01-12 2012 under the TimeIntervals tab:

  • Click on the checkbox at the far right next to the first row of thetime 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 2012-08-01T00:00:00.
  • In the same way, modify the upper boundary of the time interval to 2012-08-31T00:00:00.

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.

 

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2.2.6: Defining the Observation Description

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

On Template Type, select now science. The existing VISIR science templates will appear. Select the template VISIR_spec_obs_LRAutoChopNod and click on Add. The template will be attached to the grid below next to the acquisition template selected and filled previously.

Several parameters have to be defined for this template. In the following we discuss each of them and justify a certain choice based on the properties of the target He3-298 and the scienctific goal of this spectroscopy OB. Since you want to chop and nod within the slit to use the full exposure time to integrate on-source, you select a parallel chop/nod direction, and the same chopping position angle and amplitude that you have selected in the acquisition template. You therefore enter:

  • Relative Chop/Nod Direction: PARALLEL (Default value)
  • Chopping Position Angle: 206
  • Chopping Amplitude: 10

Several bad pixels or cosmics will produce an errornous response at some parts of the array. Therefore you want to avoid thetarget's signal falling permanently on a bad pixel and you chooseto jitter on the nod positions by setting:

  • Random Jitter Box Width: 2

After using the exposure time calculator for VISIR in spectroscopy mode, you know that 500sec of total integration time is needed on He3-298 in order to reach the signal to noise ratio you want. Thus,

  • Total integration time: 500

If you followed all the indications given so far, the View OB window should look like this now.

 

The only other thing that you should really do at this point is to check the execution time for this OB. Next to the Execution Time label you will find a button labeled Recalculate. Click on this button to calculate the execution time for your OB.

This (almost) completes your first OB! You can now close the View OB window and you are left with the P2PP main GUI. In there, you should see an entry under Summaries with the following contents:

  • Name: He3-298-spec
  • Status: (P)artiallyDefined
  • Target: He3-298
  • OD: Spectroscopy-N
  • CS: He3-298-SpecCons
  • Acquisition: VISIR_spec_acq_MoveToSlit
  • FindingCharts: (0)

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

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2.2.7:Attaching Finding Charts

The last thing to do, which finishes the preparation of a single OB, is to attach the respective Finding Chart(s) to the OB. The Finding Charts must be prepared as jpeg-files and must fulfillall general and VISIR-specific requirements for finding charts. 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(I)], which you called 60.A-9253I.he3-298.jpg, 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-9253I.he3-298.jpg and finally click on the Attach Finding Charts button (you could select more than oneFinding 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..

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3: Finishing the preparation and submitting the OBs

With the completion of the OBs, we consider the examplesdeveloped 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 imaging observation and one spectroscopic observation ends here. For the preparation of the Phase 2 material for a whole run, however, more OBs may have to be created. Furthermore, the complete Phase 2 material includes also a README file for each run. The README file is an integral part of P2PP, it is written within the P2PP environment and also 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 Alert ESO that all the phase 2 materials have been subnmitted button at the top of the main P2PP window.

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(I) 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.

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