CRIRES P2PP Tutorial

This tutorial provides a step-by-step example of the preparation of a set of Observation Blocks (OBs) with CRIRES, the cryogenic high-resolution infrared echelle spectrograph on UT1 (Antu) of the VLT. The specifics of this tutorial pertain to the preparation of OBs for Period 82 onwards. To follow it, you should have a P2PP installation on your computer and be familiar with the essentials of the use of the software. Please refer to the instructions in order to install it, 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 OBs for two simple example observing runs.

Case A consists of spectroscopy of a bright point source under good seeing conditions. Let's take the M-star AU Mic (RA (2000) = 20:45:09.5, Dec (2000) = -31:20:27) for which a high precision radial velocity shall be determined to search for faint companions. The target star also serves as Adaptive Optics (AO) guide star as well as the slit viewer (SV) guide star for fine guiding.

Case B describes the spectroscopy of a faint quasar for which no AO performance is needed but a nearby bright guide star is defined as reference target. Let's take for example the quasar HE 0251-5550 at redshift z>2 as target (RA (2000) = 02:52:40.1, Dec (2000) = -55:38:32) and a 11th magnitude star as guide star for this observation (RA (2000) = 02:52:37.24, Dec (2000) = -55:40:43.0, R=11.5). NaID and/or CaII H-K absorption lines shall be detected in the quasar's spectrum.

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 CRIRES.

1: Getting started

The Phase II 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 CRIRES. Therefore, you decide to start preparing your Phase II material.

First, you collect all the necessary documentation:

• The CRIRES User Manual.
• The VLT Service Mode Guidelines.
• The P2PP Documentation referred to above.

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

2: Case A: a bright star

You decide to start with the bright star as first science case. So, off you go to define those observations.

2.1: 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 now have their own P2PP login data can still use P2PP and prepare example OBs. You cannot use it to prepare actual OBs intended to be executed.

After 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 CRIRES Tutorial run, 60.A-9253(K). 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 CRIRES 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

Let this be the OB for spectroscopy in the J, H and K band of your bright star. Since this OB will be the JHK observation of AU Mic, you can call the OB 'AU Mic - JHK'. Type this name in the Name field.

Next, assign this OB a priority. Since for purposes of this tutorial the spectroscopy of the bright star is more important than the one for the faint target (Case B), select 2 from the dropdown Priority menu.

It may be useful in many cases to have an easy way of identifying an observation description (OD), like when having observations of a number of targets performed with identical instrument configuration and exposure times. 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 example OB, the OD will consist of a sequence of three spectroscopic exposures in the J, H, and K bands. We can thus appropriately name it JHK spectroscopy. Enter this name in the OD Name field.

Next, 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 (but see the reference below to the Calibration Requirements field), ...). For this tutorial you can try it out by entering the text "CRIRES Tutorial Spectroscopy OB".

Finally, the Instrument Comments field should be used for some information you have to pass to the staff on Paranal. In the case of CRIRES this is the expected signal-to-noise and magnitude of your target, and the magnitudes of the AO and SV guide stars. Since in this case the target also is the AO and SV guide star, simply enter "S/N=100@1580nm; J_OBJ=5.4; H_OBJ=4.8; K_OBJ=4.5".

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2.1.2: Defining the acquisition template

The first template that must be part of any 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 the two acquisition templates available for CRIRES in the Template list next to it.

After reading the description of the templates in the CRIRES User Manual, you have determined that the CRIRES_spec_acq_NGS template is the appropriate one for this observation because you want to use AO. 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. These are required for the pointing and tracking of the telescope, the centering of the target in the slit, the setting of the derotator mode, and for acquiring the natural guide star (NGS) and close the loop of the Adaptive Optics (AO) system.

Since your target also is the AO guide as well as SV guide star, the boxes Target = AO Guide Star and SV Guide Star = AO Guide Star should remain checked. The information for the AO guide star that has to be filled in are its coordinates and its B-R color. The color is needed to estimate the flux in R that reaches the wave front sensor (WFS) of the AO system. In the case of AU Mic, B-R = 2.36 (obtained from a Vizier query). The box Use the last sky measurement for the WFS can remain unchecked. Only for very bright AO guide stars a sky measurement is recommended.

The parameters of the SV guide star and the telescope guide star should stay to their default values. Only for faint guide stars a new sky measurement for the SV is recommended (uncheck the box Use the last sky measurement for the SV in this case). The DIT and NDIT of the SV camera are determined automatically by the system.

We are coming to the point where some critical instrument parameters have to be set. Our target is a point source which can be observed using any orientation of the slit. In this case the ELEV is recommended. In ELEV mode, the slit is constantly aligned with the parallactic angle in order to reduce slit loss introduced by differential refraction. This is important because the SV guiding will be performed in the J band whereas the observations are done in the J, H and K band. To select the ELEV mode, click on the red NODEFAULT field next to the Derotator: Mode box and select ELEV. The Position angle can, of course, not be chosen in this mode and stays at its default value 0.0. Next, the slit width and the wavelength range have to be chosen. Since we aim at the highest possible resolution the minimum slit width of 0.2 arcsec is appropriate. Let's assume that we like to cover the wavelength range 1238.8-1266.7 nm in the J band. The reference wavelength that corresponds to this wavelength range is 1256.4 nm (see Table 4 of the CRIRES User Manual). The grating order has only to be defined if the reference wavelength is not unique (see Table 7 of the CRIRES User Manual).

In summary, the set of parameters that you choose in your acquisition template is thus:

• Target = AO Guide Star: box remains checked
• RA of AO guide star: 20:45:09.5 or leave it to 0
• DEC of AO guide star: -31:20:27.0 or leave it to 0
• AO guide star: B-R color value: 2.36
• AO guide star: FWHM (arcsec): 0.0
• AO guide star: Minimum S/N: 1000
• Use the last sky measurement for the WFS: box remains unchecked
• WFS Alpha sky offset (arcsec): 4.0
• WFS Delta sky offset (arcsec): 4.0
• SV Guide Star = AO Guide Star: box remains checked
• Use the last sky measurement for the SV: box remains checked
• RA offset to sky: 30.0
• DEC offset to sky: 30.0
• Telescope guide star selection: CATALOGUE
• RA of telescope guide star: 0.0
• DEC of telescope guide star: 0.0
• Differential tracking in RA: 0.0
• Differential tracking in DEC: 0.0
• RA offset between target and SV guide star: 0.0
• DEC offset between target and SV guide star: 0.0
• Derotator: Mode: ELEV
• Position angle: 0.0
• Entrance slit width: 0.2
• Reference wavelength: 1256.4
• Grating order: 0

The zero values of the Differential tracking parameters are due to the fact that your target is not a Solar System one needing differential tracking.

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

2.1.3: Inserting Target Information

Let us for a moment take a break from inserting templates into this OB.

The coordinates (including epoch and equinox) of the science target have to be defined in the Target-tabbed subpanel on the bottom of the window. You can give the target the name "AU Mic" and should enter the target coordinates in the Right ascension and Declination boxes. Proper motions and differential tracking are not needed in our case. The only entry in the right side of the subpanel which may be edited is the Class to which this object belongs, for archival purposes. In this case, choose just Star.

After inserting the values the sub-panel looks 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 Constraint Set for your OBs. You can do this by clicking on the Constraint Set tab and filling the entries under it:

• 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 spectroscopic observations, you type Spectroscopy constraints in the Name field.
• Since you are not interested in achieving accurate flux calibration of your spectra, you request Variable, thin cirrus conditions in the Sky Transparency entry.
• You like to have a very good AO performance. Therefore you should choose a good seeing. Enter 0.6 as value in the Seeing field.
• The Strehl ratio defines the performance of the AO system. This value is an output of the CRIRES Exposure Time Calculator (ETC). In our case a value of 40.0 is appropriate for the J band. Enter this in the Strehl (%) field.
• Set the Airmass to 1.5, to ensure that your observations are not carried out at too low an elevation that would affect the AO performance.
• Since you are doing high resolution spectroscopy of a bright target in the NIR, the lunar illumination has basically no influence. You should require 1.0 for the Lunar Illumination and 30 degrees for the Moon Angular Distance (smaller values might cause problems linked to the telescope guiding or AO system).

Your Constraint Set panel should look like this after entering the values:

Note that in your Phase I proposal you already specified some of these constraints (seeing, lunar illumination, transparency). You must make sure that none of the constraints specified in Phase II is more stringent than the corresponding one specified at Phase I.

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2.1.5: Setting the time intervals

We will assume now that the spectroscopic observations that you are defining are part of a spectroscopic monitoring program of AU Mic and that, to ensure that you have the spectroscopic shifts properly sampled, this particular OB needs to be executed during September or October. You can specify this 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 2008-09-01T00:00:00.
• In the same way, modify the upper boundary of the time interval to 2008-09-30T00:00:00.

The panel looks like this now:

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.

The Calibration Requirements field is a free text field whose contents is self-explanatory. In this example, you might want to enter "A telluric standard should be taken after this OB.".

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2.1.6:  Defining the Observation Description

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

After checking with the manual and considering the scientific requirements of your program, you have decided to execute the observations using two nodding cycles (pattern ABBA) and jittering in a 5 arcsec box. The right template is the CRIRES_spec_obs_AutoNodOnSlit template. To select it, choose in the Template Type menu science. Then select the template and click on Add. The template will be attached to the grid below next to the acquisition template selected and filled previously.

Given the flux of your source and the advice on the duration of the individual DITs in each filter as given in the User Manual and checked with the Exposure Time Calculator (ETC), you decide that an appropriate choice of integration parameters is such that at each nodding position you obtain 15 exposures (NDIT) of 10 sec (DIT) in the J, H, and K band. A gas cell is not needed during the observations. The first CRIRES_spec_obs_AutoNodOnSlit template (the observation in J) thus has the following parameters:

• DIT: 10
• NDIT: 15
• Number of exposures per nodding position: 1
• Number of nodding cycles: 2
• Nod throw along the slit: 10
• Jitter width: 5
• Reference wavelength: 1256.4
• Grating order: 0
• Gas cell: FREE

For the observations in the H and K band, we assume that the desired wavelength ranges are 1571.2-1610.7 nm and 2254.0-2304.6 nm, respectively. The corresponding reference wavelengths are 1596.9 and 2287.0 nm. Both wavelength settings are unique. No grating order has to be defined. You can select again the same template, Add it, and fill the parameters in the same way as done for the template in the J band. Alternatively, 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 (thereby selecting that column), then clicking on the Duplicate Col: 4 button on the upper right, and then clicking again on the same button. In this way, you will have produced two identical copies of the first science template in which you should now only edit the parameters that change from template to template:

• Reference wavelength must be changed to 1596.9 for the H band and 2287.0 for the K band.

The only other thing that you should really do at this point is to check the execution time for this OB. Unlike in past Periods when this was automatically done as you built up OBs, from Period 72 on you must click a button to update the displayed time. The fact that the displayed time does not reflect 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 00:56:34, that is, well under the 1 hour execution time limit.

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

and you should see an entry under Summaries in the P2PP main GUI with the following contents:

• Name: AU Mic - JHK
• Dbaseid: 0
• Status: (P)artiallyDefined
• Target: AU Mic
• OD: JHK spectroscopy
• CS: Spectroscopy constraints
• Acquisition: CRIRES_spec_acq_NGS
• FindingCharts: (0)
• EphemerisFile:

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

At this point you may notice the (0) under the heading of FindingCharts. This is because you have not attached any Finding Charts to the OB. Following the general rules and CRIRES-specific rules for Finding Chart generation, you make your Finding Chart(s). The jpg file(s) should then be on your local disk, and you attach them one by one to the OB by highlighting the OB, clicking on the Finding Charts button on the top, and selecting Attach Finding Charts from the pull-down menu. This gives you a browser window, in which you navigate to the correct directory and select the file(s). The P2PP Finding Chart Tutorial gives more advice on how to attach Finding Charts within P2PP.

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3: Case B: a faint target

When planning your second observing run, you realized that your spectroscopic target (the quasar) is too faint to serve as AO or SV guide star. Anyway, AO performance is not needed for this program and also the resolution can be quite moderate. A slit width of 0.6 arcsec is needed to get enough flux and a seeing of 0.8 arcsec can be tolerated. No bright reference target is found within 40 arcsec of the science target. Thus no fine guiding with the SV can be performed. However, a quite bright star (R=11.5 mag) some 2.2 arcmin away from the quasar shall serve as telescope guide star.
Since 0.4 arcsec is the maximum allowed slit width, you have to send a Waiver Request with a thorough scientific justification in order to use a 0.6 arcsec slit instead of a 0.4 arcsec slit. In your case, guiding on a SV star is not needed, thus we assume that a 0.6 arcsec is not critical and that the waiver was accepted.

The interesting Na and Ca absorption lines are expected at 1967.5 and 1969.5 nm (Na) and 1314.0 and 1325.7 nm (Ca). These wavelengths can be covered by using three different wavelength settings in the H band. The total execution time is expected to be much longer than 1 hour. So the different wavelength setting can not be put into one OB.

Most steps that you should follow to define the OB are analogous to those that you followed when preparing the AU Mic - JHK OB before, although there are fewer parameters in the acquistion template this time.

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3.1: P2PP

It is assumed that you already started P2PP and have chosen the CRIRES Tutorial run, 60.A-9253(K). If this is not the case please have a look at point 2.1.

Define a new OB by clicking on the New icon on the upper left side of the P2PP main GUI. Then open the View OB window by choosing the View icon. This is the window where you will define the contents of your next OB.

3.1.1: Filling in the Basic Information

Let this be the OB for the Na lines around 1968 nm. You might call the OB 'HE 0251-5550 - Na'. Type this name in the Name field.

Next, assign this OB a priority. You might think that the Na lines are the most important ones, thus the OB should have Priority 1. Select 1 from the dropdown Priority menu.

The OD Name in this case shall be H spectroscopy.

Finally, the User Comments field and the Instrument Comments can/should be used. No information is needed in the User Comments for this OB. In the Instrument Comments you should give the expected signal-to-noise and magnitude of you target. Enter "S/N=20@1968nm; H_OBJ=14.6".

The top of the View OB window should now look like this:

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3.1.2:  Defining the acquisition template

The first template is the acquisition template. Since no AO is needed, the right template is CRIRES_spec_acq_NoAO. Highlight this template and then click on the Add button next to it.

Although your target is faint you might try to use it as SV guide star. For this you should uncheck the Use the last sky measurement for the SV box to get a new sky measurement. For the Telescope guide star selection choose SETUPFILE from the pull-down menu. Then enter the coordinates of the guide star into the telescope guide star boxes.

The Derotator: Mode should be set again to ELEV mode, Entrance slit width to 0.6 arcsec, and the Reference wavelength to 1976.9 nm.

The set of parameters that you choose in your acquisition template is thus:

• Use the last sky measurement for the SV: uncheck box
• RA offset to sky: 30.0
• DEC offset to sky: 30.0
• Telescope guide star selection: SETUPFILE
• RA of telescope guide star: 02:52:37.24
• DEC of telescope guide star: -55:40:43.0
• Differential tracking in RA: 0.0
• Differential tracking in DEC: 0.0
• RA offset between target and SV guide star: 0.0
• DEC offset between target and SV guide star: 0.0
• Derotator: Mode: ELEV
• Position angle: 0.0
• Entrance slit width: 0.6
• Reference wavelength: 1976.9
• Grating order: 0

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

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3.1.3: Inserting Target Information

You can give the target the name "HE 0251-5550" and should enter the target coordinates in the Right ascension and Declination boxes. Proper motions and differential tracking are not needed in our case. The only entry in the right side of the subpanel which may be edited is the Class to which this object belongs, for archival purposes. In this case, choose DLy-alpha_ALS for a damped Lyman alpha system.

After inserting the values the sub-panel looks like this:

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3.1.4: Setting the Constraint Set

We again 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 tab and filling the entries under it:

• First, give a descriptive name to the constraint set about to be defined. For example, type Quasar spectroscopy constraints in the Name field.
• Since you are not interested in achieving accurate flux calibration of your spectra, you request Variable, thin cirrus conditions in the Sky Transparency entry.
• Very good seeing is not needed. 0.8 arcsec should be sufficient to get enough flux into the 0.6 arcsec slit. Enter 0.8 as value in the Seeing field.
• The Strehl ratio does not apply since no AO is requested. It should be left to the default value 0.0.
• The Airmass might be set to 2.0, since no AO is needed.
• Since you are doing high resolution spectroscopy of a target in the NIR, the lunar illumination has very little influence. You should require 1.0 for the Lunar Illumination and 30 degrees for the Moon Angular Distance (smaller values might cause problems linked to the telescope guiding).

Your Constraint Set panel should look like this after entering the values:

Note that in your Phase I proposal you already specified some of these constraints (seeing, lunar illumination, transparency). You must make sure that none of the constraints specified in Phase II is more stringent than the corresponding one specified at Phase I.

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3.1.5: Setting the time intervals

These time no time constraints are needed. No values have to be entered.

The Calibration Requirements field is a free text field whose contents is self-explanatory. We will leave it blank in this example.

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3.1.6:  Defining the Observation Description

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

The faint target needs long exposure times. After consulting the exposure time calculator you find that DITs of 300 sec and a NDIT of 12 is needed to reach the desired signal-to-noise. One nodding cycle (AB) is sufficient to handle the sky subtraction, but at each nodding position the exposures shall be jittered in a 5 arcsec box. Thus a DIT of 300 sec, a NDIT of 2 and 3 as Number of exposures per nodding position is chosen as observing strategy. No gas cell is needed for this observation.

Again, the only template to choose is the CRIRES_spec_obs_AutoNodOnSlit template. This time it should have the following parameters:

• DIT: 300
• NDIT: 2
• Number of exposures per nodding position: 3
• Number of nodding cycles: 1
• Nod throw along the slit: 10
• Jitter width: 5
• Reference wavelength: 1976.9
• Grating order: 0
• Gas cell: FREE

This completes your first OB of your slcond run! If you followed all the indications given so far, the View OB window should look like this now:

and you should see an entry under Summaries in the P2PP main GUI with the following contents:

• Name: HE 0251-5550 - Na
• Dbaseid: 0
• Status: (P)artiallyDefined
• Target: HE 0251-5550
• OD: H spectroscopy
• CS: Quasar spectroscopy constraints
• Acquisition: CRIRES_spec_acq_NoAO
• FindingCharts: (0)
• EphemerisFile:

You can reshape the columns as indicated in the P2PP User Manual to view the full contents of each entry. Finding Chart generation and attachment to the OB can be done as described above.

Next, you can check the Execution Time clicking on the Recalc ExecTime button. It turns out to be 1:15:49 hours, much longer than allowed for an OB in service mode. Either your scientific justification for such a long OB is very strong and you decide to try getting approval for this through a Waiver Request, or you feel that you can simply divide this OB into two smaller ones (with smaller DITs and/or NDITs) to achieve the same scientific goal(s).

To complete your second run you have to define further OBs for the wavelength settings with the Ca lines. The reference wavelengths are 1329.9 and 1333.4 inm for the lines at 1314.0 and 1325.7 nm, respectively. The ETC tells you that for this regions a NDIT of 48 is needed for the same DIT of 300 sec as for the previous OB. Thus four 1:15:49 hours OBs have to be defined for each of the wavelength settings. To make life easier, you decide to simply duplicate the previously made spectroscopic OB (HE 0251-5550 - Na) and use the copy as a starting point. To do this select the appropriate OB in the P2PP main GUI and press the Duplicate button next to the New button on the upper left. Then press View and you can change the relevant parameter(s) (Reference wavelength, DIT, NDIT, etc.) in the science template. In total, 9 OBs are necessary to defime the second run. Let's hope that your waivers about the long execution time are successful!

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4: Finishing the preparation and submitting the OBs

With the completion of the OBs for case A and B, we consider the examples developed in this tutorial to be finished. The P2PP main GUI displays the 10 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.

At this point, for the case of a real Service Mode Run only you should click on the p2pp-submit button on the P2PP GUI. This has the effect of sending a signal email to your Support Scientist that OBs have been checked in to the ESO Repository.

Again for the case of a real Service Mode Run only you should also view/edit/check-in a corresponding README file. The P2PP README file Tutorial gives more advice on how to do this.

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(K) 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 three 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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