ISAAC P2PP Tutorial

Goal of the run

1- Getting started

The Phase 2 process begins when you receive an email from the ESO Visiting Astronomers Section communicating to you that the allocation of time for the coming period has been finalized and that the results can be consulted in the corresponding Web page. The communication from ESO contains a login ID and password that you need in order to consult that Web page, but it is also your ID and password for the use of P2PP. You follow the instructions given by ESO and find that time was allocated to your run with ISAAC. Therefore, you decide to start preparing your Phase 2 material.

• The ISAAC User Manual
• The Service Mode instructions for VLT and ESO-MPI 2.2m telescope.
• The P2PP Documentation referred to above.
• The ISAAC specific P2PP instructions

• 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 for which you are PI.

Select the folder corresponding to the ISAAC Tutorial run, 60.A-9252(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 ISAAC run.

You can now start defining your OBs.

2- Creating the first OB

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:

Setting the target information

Let this be the OB for J, H and Ks-band imaging of your target. Since this OB will be the JHKs observation of NGC 6611, you could choose a descriptive name like OB 'NGC 6611 - JHKs'. Type this name in the Name entry near the top of the View window.

• In the Name field under the Target tab at the bottom, type the target name (NGC 6611)
• In the Right Ascension, Declination fields, type the coordinates given above
• Since the coordinates are given for both epoch and equinox J2000, leave these fields with their default values
• You can give also the Class to which this object belongs, for archival purposes. In this case, choose Assoc* (stellar association).
• The proper motion of this target is negligible for the purposes of this example, and differential tracking of the telescope is not needed since this is not a moving Solar System target. Therefore, you can leave the last four fields in the Target tab set to their default values of zero.

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 imaging observations, you type Imaging constraints in the Name field.
• Since you wish to be able to determine accurate fluxes from your images, you request Photometric conditions in the Sky Transparency entry.
• Since you need moderately good quality in your images, you specify 0.8 as the value of the Seeing field.
• The Strehl ratio applies to observations with NACO only, so leave the default value there.
• Set the Airmass to 2.0, to ensure that your observations are not carried out at too low an elevation.
• 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 that in your Phase 1 proposal you already specified some of these constraints (lunar illumination, seeing, transparency). You must make sure that none of the constraints specified in Phase 2 is more stringent than the corresponding one specified at Phase 1.

Setting the time intervals

We will assume now that the imaging observations that you are defining are part of a photometric monitoring program of NGC 6611 and that, to ensure that you have the light curves properly sampled, this particular OB needs to be executed between June and July 2003. 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 2003-06-01T00:00:00.
• In the same way, modify the upper boundary of the time interval to 2003-08-01T00:00:00.

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.

The User Comments (in top section) and Calibration Requirements fields are free text fields whose contents are self-explanatory. We will leave them blank in this example, but generally it is useful to mention in the User Comments any peculiarities concerning the execution of an OB. If this is lengthy or complicated, add a reference to the README file, where you should explain it in detail.

Defining the acquisition template

The first template that must be part of any OB that requires a definite pointing 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 ISAAC in the Template list next to it.

After reading the description of the templates in the ISAAC User Manual, you have determined that the ISAACSW_img_acq_MoveToPixel template, suitable for imaging with the Hawaii (Short wavelength) array, template is the most suitable one for this particular observation. You thus click on this template in the Template list, and then on the Add button next to it.

You need to decide now on the acquisition parameters. This acquisition template sets a filter and takes an OFF frame at an offset of Alpha offset and Delta offset arcseconds from the target position for sky subtraction purposes. Then it takes exposures in open loop presenting on the Real Time Display at the telescope console the image obtained after DET.NDIT integrations of DET.DIT seconds each, minus the OFF frame. This allows the identification of the target field. Since you have decided to obtain the images in the J, H and Ks filters in this order, some time will be saved if you set the J filter already in the acquisition template, so that the filter setup is already done by the time that the first science observation starts. Moreover, since the brightest stars in this field are fairly bright, the images for acquisition do not need to go very deep, meaning that DET.DIT and DET.NDIT can be small; say, 5 sec and 1 exposure respectively. As to the other parameters, you decide that the default orientation of the frames, with North at the top, is perfectly fine for your purposes. The set of parameters that you choose in your acquisition template is thus:

• DET.DIT (sec): 5
• DET.NDIT: 1
• Alpha offset (arcsec): 10
• Delta offset (arcsec): 10
• Add Velocity Alpha: 0.
• Add Delta Velocity: 0.
• Position Angle on Sky (degrees): 0. (i.e. North on top)
• Preset Telescope ? (T/F)checked (i.e., True)
• SW Filter wheel 1: J
• SW Filter wheel 2: open

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

If you specify one of the parameters outside the allowed range, it turns red. The OB is not considered valid (and you will not be allowed to check it in (see Section 6) unless all parameters are defined within allowed ranges. The acquisition template is now complete.

Defining the Observation Description

Once the acquisition is completed, the science observation begins. The science observation is defined in a set of one or more templates that form the Observation Description, or OD for short.

It may be useful in many cases to have an easy way of identifying an OD, like when having observations of a number of targets performed with identical instrument configuration and exposure times. The 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 jittered exposures through the J, H and Ks filters. We can thus appropriately name it JHKs Autojitter. We enter this name in the OD Name field.

Next, the templates need to be attached. After checking with the manual and considering the scientific requirements of your program, you have decided to execute the observations with the Hawaii (SW) array (you selected the detector already during your submission of the Phase1 proposal). You will apply a random jitter pattern within a 20 arcsec box, using the object frames themselves to construct a sky frame for background subtraction. You conclude that the ISAACSW_img_obs_AutoJitter template is the most suitable one. On Template Type, select now science. The existing ISAAC science templates will appear. Select the chosen one, ISAACSW_img_obs_AutoJitter, and click on Add. The template will be attached to the grid below next to the acquisition template selected and filled previously.

You want the brightest source in your field to remain within the linear part of the response of the Hawaii array, 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 700s per filter, and that DITs should not exceed 45s in J and 12s in H and K (see Table 23 of the ISAAC User Manual). The time spent at a jitter position (=DIT * NDIT) should not exceed 180s in J and 120s in K, respectively. You decide to set DIT to 28s and NDIT to 3 for J band, which results in 8 jitter positions (Number of Exposures), a reasonable number (it should not be too low). For H and K band, you rather want to set DIT to 11s, NDIT to 8, which again results in 8 jitter positions.

Furthermore, you decide to start the jitter in each filter at the reference position given by the preset coordinates, rather than at the last position observed in the previous template. The first ISAACSW_img_obs_AutoJitter template (the observation in J) thus has the following parameters:

• DET.DIT (sec): 28
• DET.NDIT: 3
• Number of Exposures: 8
• Jitter Box Width (arcsec): 20
• Return to Origin ? (T/F): checked (i.e., True) (the telescope will thus return to the initial position after the execution of the template)
• SW Filter wheel 1: J
• SW Filter wheel 2: open

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:

• DET.DIT (sec): 28 must be changed to DET.DIT (sec): 11
• DET.NDIT: 3 must be changed to DET.NDIT: 8
• SW Filter wheel 1: J must be changed to H

In a similar manner, you create your K-band OD by duplicating the H-band OD and modifying the filter entry.

This completes your first OB! If you followed all the instructions 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: NGC 6611 - JHKs
• Dbaseid: 0
• Status: (P)artiallyDefined
• Target: NGC 6611
• OD: JHKs Autojitter
• CS: Imaging constraints
• Acquisition: ISAACSW_img_acq_MoveToPixel

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

You should now check the execution time of your OB, to make sure it is shorter than 1 hour. This is done by clicking on the Recalc Exec Time button to the right of the main GUI window (or by selecting Reports -> Execution Time -> Selected in the main GUI window). The calculated time includes overheads, and it is 00:59:48. Whenever the Execution Time indicated in the top left section of the main window is not up-to-date, a little star appears to the left of "Execution Time".

Now is maybe also the time to check if your OB contains any errors which are easy to find via a coded script. This is done by selecting Reports -> Verify -> Selected in the main GUI window, and it checks for template mismatches, filter settings, and the like. If it reports an "ERROR", this will prevent you from checking in the OB to the ESO database, and you will have to correct it. A "WARNING" or information means that you set a parameter or combination of parameters in an unusual way. You should confirm for yourself that this is what you really want. If the reason for this unusual setup is not obvious to the future observer from the context, it might be useful to add a remark to the "README" file.

The result of running the verification is shown here:

The WARNING about several distinct filters was implemented to warn users who might inadvertently changed a filter in their OB. In your case, this is exactly what you want to do, so you can ignore it. Otherwise, the OB is fine.

3- Defining the second imaging OB

Let us assume now that you want to perform in addition narrow-band imaging through the filter centered on the 2.122 microns transition of the hydrogen molecule, named NB_2.13 in the list of available filters. Since a long exposure will be needed in this case and the OB for the JHKs imaging that you just completed would already take about 1 hour to execute at the telescope, you will have to define a separate OB for the observation in this filter (the maximum allowed duration of any one OB is one hour).

Since your target is the same, as well as the acquisition template to be used and the kind of science template to be used in the OD, you will complete this part faster if you duplicate the OB you just created and modify its contents as needed. To do this, select the imaging OB just produced in the main GUI window and click on the Duplicate button (the second one in the row of icons on the top right). This creates an exact copy of the OB in which only the name (now with the -0 suffix added) is modified.

Like before, click on the View icon to be able to view the full contents of the OB and modify it.

You can first modify the name of the OB and OD, for which we now suggest:

• Name: NGC 6611 - H2
• OD Name: H2 Autojitter

Since our targets may be too faint to identify correctly in the narrowband H2 filter in a short integration, we choose to do the acquisition in a broad-band filter, e.g. Ks, to simplify the identification of the field. The first filter wheel should thus be set to Ks, and the second one should be left open. This is thus the contents of the acquisition template:

• DET.DIT (sec): 5
• DET.NDIT: 1
• Alpha offset (arcsec): 10
• Delta offset (arcsec): 10
• Add Velocity Alpha: 0.
• Add Delta Velocity: 0.
• Position Angle on Sky (degrees): 0.
• Preset Telescope ? (T/F)checked (i.e., True)
• SW Filter wheen 1: Ks
• SW Filter wheen 2: open

For the observations themselves, we will need two jitter templates: one for the observation in the NB_2.13 (H2) filter (ISAACSW_img_obs_AutojitterOffset), and one in the NB_2.09 filter (ISAACSW_img_obs_Autojitter), which we will use as a continuum reference. We are using the ISAACSW_img_obs_AutojitterOffset template for the H2 line observations, because we are expecting extended emission, which would compromise proper background subtraction using a sky frame constructed from frames which were just jittered by less than 20 arcsec.

We can start by deleting two of the templates in the OD (the autojitter in H and Ks), one by one, by clicking on one of their entries and then clicking on the Delete Col button on the upper right. You can be sure you have selected the template that you wish to delete by checking the corresponding column number that will appear in the Delete Col button.

After doing this, your OB contains now only the science templates corresponding to the autojitter observations in J. Let us assume that the most adequate exposure parameters for the new H2 observation correspond to a jitter of 8 positions, each with two 60 second integrations. The contents of the ISAACSW_img_obs_Autojitter template thus becomes:

• DET.DIT (sec): 80
• DET.NDIT: 2
• Number of Exposures: 8
• Jitter Box Width (arcsec): 60
• Return to Origin ? (T/F): checked (i.e., True)
• SW Filter wheel 1: NB_2.09
• SW Filter wheel 2: open

The contents of the ISAACSW_img_obs_AutojitterOffset template will be similar, but you have applied a Sky Throw of 180 arcsec, in order to be sure to avoid extended H2 emission. It will move the telescope to a random position located on a circle with the specified radius. In principle, you can define different NDITs for the Object and the Sky positions, but we set them both to 2. The Rotate Pupil parameter should be checked if one wants to have the pupil rotated for the sky positions, which helps to avoid pupil ghosts. The Number of AB or BA cycles replaces the Number of Exposures parameter: One cycle corresponds to two positions, so for 8 exposures, we need to set this to 4.

• DET.DIT (sec): 80
• Jitter Box Width (arcsec): 20
• Return to Origin ? (T/F): checked (i.e., True)
• Sky Offset Throw (arcsec): 180
• Rotate Pupil ?: checked (i.e., True)
• Number of AB or BA cycles: 4
• NDIT for the Object positions: 2
• NDIT for the Sky positions: 2
• SW Filter wheel 1: open
• SW Filter wheel 2: NB_2.13

The contents under the Target tab can be left unchanged. If the same constraints as defined before for the JHKs imaging OB are appropriate for the H2 observation, you can also leave the contents under the Constraint Set tab unchanged.

If this OB does not have any timing constraint, you must edit the contents under the Time intervals since the JHKs OB did have. To remove the time constraint, you only need to uncheck any box next to the entries defining the boundaries of the time window that was previously checked. You do not need to restore the starting and ending times of the time window to its default values.

This is what the contents of the finished NGC 6611 - H2 OB should look like:

4- Defining a spectroscopic OB

To complete this ISAAC tutorial with an exercise on another instrument mode, we will add a spectroscopic OB to our hypothetical run.

The purpose of this OB will be to obtain a medium resolution spectrum of the core of NGC 6611 in the region around the Brackett alpha line of Hydrogen at 4.05 microns. We start by generating a new OB from scratch (icon New in the P2PP main GUI) and get ready to edit its contents (icon View). We can name this OB NGC 6611 spectrum, and its OD spectroscopy.

Spectroscopic acquisition

Next, we proceed to adding the acquisition template. Since we want to observe at wavelengths longer than 2.5 microns, we will have to use the Aladdin (Long Wavelength) Array for both the acquisition and the observation itself. You may note at this point that, unlike you may have expected, there is no ISAACLW_spec... template for spectroscopic acquisition. This is due to the fact that placing the object at the position of the slit (which is known to the instrument from calibration procedures carried out by the observatory staff) is done by imaging the field, and thus the acquisition template is actually of the img type. As described in the ISAAC manual, the template to be used for spectroscopic acquisition with the Aladdin array is ISAACLW_img_acq_MoveToSlit.

Some of the parameters to be defined in this template are already familiar from previous examples. We will assume that the acquisition is made with images through the M_NB filter with chopping with a chop throw of 20 arcseconds parallel to the slit, and that the slit to be used is the one with 0.6 arcsec width (slit_0.6).

The parameters Alpha Offset from Ref. Star and Delta Offset from Ref. Star offer the possibility of accurately presetting the telescope on a bright reference target close to the position of the science target, and then giving an offset to the telescope before the science observation starts so that it moves to the position of the science target. This is useful in case of faint targets that may not be visible in the acquisition image or require an excessively long acquisition time. In our example, the science target is bright enough and we do not need to use this indirect acquisition, so we leave these offset fields at their default zero values.

For practical purposes, this template also offers the possibility of actually presetting the telescope to the desired position, or just performing the setup of the instrument without sending the preset order to the telescope (parameter Preset Telescope ? (T/F)). Skipping the telescope preset saves some time at execution if the telescope was already at the target position. At the time of preparing the observations, either in Visitor or Service Mode, this flag should always be set to True.

• Preset Telescope ? (F/T): checked (i.e., True)
• Chop Throw (arcsec): 20
• Number of chop cycles: 1
• ChopNod PARA or PERP to Slit: PARA
• Alpha offset from Ref. Star: 0
• Delta offset from Ref. Star: 0
• Add Velocity Alpha: 0.
• Add Delta Velocity: 0.
• Position Angle on Sky (degrees): 0.
• LW Filter wheel 1: M_NB
• LW Filter wheel 2: open
• Slit: slit_0.6

Spectroscopic OD

As explained in the ISAAC User Manual, there are three templates for LW spectroscopic observations with ISAAC, each one allowing the use of either of two detector readout modes. AutoChopNod, suitable for automatic chopping and nodding along the slit, moves the target between the proximities of two positions along the slit and will be our choice here.

After considering the spatial extent of our target, we decide to carry out our observations using a chop throw of 20 arcseconds parallel to the slit (which keeps the object in the slit during all exposures and therefore optimizes the SNR), and decide on a jitter box width of 10 arcseconds. The dispersion element to be used is defined in the Instrument Mode entry: in our case, we select LWS3-MR, which will produce a medium resolution spectrum. For the central wavelength, we select the wavelength of the Brackett alpha line, 4.05 microns. The slit to be used must be consistent with the one selected in the acquisition template, as different slits project on different positions in the detector. Since the individual detector integration times are dominated by the (variable) sky background at the long wavelength at which we are observing, the only other parameter we have to specify is the total integration time in minutes. Using the information found in the ISAAC User Manual, we decide that a total integration of 30 minutes should produce a sufficient S/N to achieve our scientific goals.

This is thus the contents of the science template that composes the OD:

• Jitter Box Width (arcsec): 10
• Return to Origin ? (T/F): checked (i.e., True)
• Chop Throw (arcsec): 20
• ChopNod PARA or PERP to Slit: PARA
• Integration time (minutes): 30
• Instrument Mode: LWS3-MR
• Slit ?: slit_0.6
• Central Wavelength (microns): 4.05

Constraint Set and Target information

Let us consider first the Constraint Set of this spectroscopic OB, and assume that the spectroscopic part of our program can be done under less favourable conditions than the imaging one, as is usually the case with spectroscopy. We define a new Constraint Set under the corresponding tab, that we name Spectroscopic constraints. We specify there Sky Transparency: Variable, thin cirrus, Seeing: 1.0, Airmass: 2.0, Lunar Illumination: 1.0, Moon Angular Distance: 30.

For the target, we could in principle click on the Target tab and type in again all the information (name, coordinates, type). But since we have already typed the information for this same target in the imaging OBs, we can just cut-and-paste information between OBs:

• Go to the P2PP main GUI, and select under Summaries one of the imaging OBs for NGC 6611 (such as for instance NGC 6611 - JHKs)
• Under the Synchronise menu, select Copy Target
• Go to the Summaries list, and click on the new spectroscopic OB to select it
• Go again to the Synchronise menu, and select now Paste to Selected OBs

You will see a dialog box asking you for confirmation of the synchronise operation. Upon clicking on Yes, the Target information in the entry corresponding to NGC 6611 - Spectrum is updated. If you go to the View OB window, you will see the Target information updated there as well, thus making the OB complete. The appearance of that window should be as follows:

5- Defining a standard star OB

When planning your observing run, you realized that the accuracy that you need for the telluric corrections makes it advisable to observe, next to the standard calibrations provided by ESO, a specific standard star near your scientific target in the sky. For this purpose you have selected the early-type star HD 170902 located at RA(2000) = 18:32:20.8, Dec(2000) = -14:38:39, and applied for time within your proposal to obtain an extra observation of this specific spectroscopy standard star. Now you must prepare the OB for this star.

In principle, this observation can be very similar to the science spectroscopic observation described in detail before. Note however that now you are defining an OB for telluric calibration purposes, and that as a consequence the appropriate ISAAC templates to use in the OD must be calibration templates, rather than science templates like before. The steps that you should follow to define the OB are analogous to those that you followed when preparing the NGC 6611 - Spectroscopy OB before (see Section 4), but now using the ISAACLW_spec_cal_AutoChopNod template instead of ISAACLW_spec_obs_AutoChopNod. The ISAACLW_spec_cal_AutoChopNod template is found under the calib menu in the Template Type list. Since the target coordinates and the template contents of this OB are both rather different from those of the previous two, it is better that you create it from scratch by clicking on the New icon in the P2PP main GUI.

The standard is a rather bright star, a total integration time of five minutes will produce a spectrum of this standard star with much better S/N than our science spectrum, and thus be suitable for calibration purposes. All other parameters in the ISAACLW_spec_cal_AutoChopNod template can/should be identical to the ones from the ISAACLW_spec_obs_AutoChopNod template used for the science observation.

In addition to selecting, adding, editing, and duplicating templates as described in detail in Section 2 and making the necessary adaptations as outlined above, you must enter the Target and Constraint Set information relevant for this case. After doing this, the contents of your OB should look as follows:

and we will assume that this completes your run.

6- Attaching the Finding Charts and the README file

Starting in P74 and P75, respectively, the submission of Finding Charts and the README file are not via ftp any more, but they are directly attached to the OBs. Please, see the respective tutorials on Finding Charts and README for instructions on how to do that.

7- Finishing the preparation and submitting the OBs

With the completion of the spectroscopic OB, we consider the examples developed in this tutorial to be finished. Now it is time to run the Verification Module again (see above) to make sure the OBs do not contain any errors, and to determine the total execution time of all OBs by selecting them all in the main GUI window and then running Reports - > Execution Time from the top bar pulldown menu. Make sure the total execution time stays within the time allocated by the OPC.

You have the possibility to influence the order in which your OBs are executed by assigning "User Priorites". Let us assume that your spectroscopy is useless if you do not get the images first. The default for the User Priority (in the top left section of the View window) is 1, the highest priority, and we leave it at the default value. For the spectroscopy and the standard star, we decrease the priority by setting it to 2. It is advisable to add a note on this in the README file, otherwise it might get overlooked.

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.

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-9252(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 four submitted OBs only, but if another user has submitted other OBs from this same account without removing them afterwards you will see them as well.
• 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.