SPHERE P2PP Tutorial
This tutorial provides a step-by-step example of the preparation of a set of Observing Blocks (OBs) with SPHERE, the the extreme adaptive optics system and coronagraphic facility at the VLT. The specifics of this tutorial pertain to the preparation of OBs from Period 94 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.
In this tutorial we will prepare an OB for simultaneous coronagraphic observations in the H-band with the imager IRDIS and the in the Y-J bands with the infrared integral field spectrograph IFS (IRDIFS mode). The target is a young stellar object named HD 141569 possessing a circumstellar disk. The target has the following coordinates: RA(2000) = 15 49 57.75, Dec(2000) = -03 55 16.3.
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 SPHERE.
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 SPHERE. 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.
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(S). 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 SPHERE run.
Once you have selected the SPHERE 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 HD 141569 and that it is an IRDIFS OB. Therefore, you choose the OB name HD 141569-irdifs. Click on the OB, and press enter, then type this name HD 141569-irdifs.
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.
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 IRDIFS. Thus, we enter the name IRDIFS in the OD Name field.
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).
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 SPHERE in the Template list next to it.
After reading the description of the templates in the User Manual, you have noticed that the SPHERE_irdifs_acq template is your choice. 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:
First we add the H and R-band magnitude of our target, necessary for the set-up of the adaptive optics system:
- Target H magnitude: 6.9
- Target R magnitude: 7.0
As we have no requirement to use a specific telescope guide star, we leave the Telescope Guide Star Selection at its default value of "Cataloue", implying that a suitable telescope guide star will automatically be selected from one of the star catalogues available at the telescope upon execution of the OB.
Next, we need to decide on the infrared coronagraph which we will use and the derotator and ADC modes. We use the standard Apodized Lyot Coronograph for service-mode observations and do not want the field to rotate during our observation:
- Infrared IRDIS coronagraph combination: N_ALC_YJH_S
- Derotator and ADC modes combination: Field
Since the acquisition template will be followed by templates in IRDIFS mode, we select IRDIFS as the Instrument Mode:
- Instrument Mode: IRDIFS
For the rest of the parameters in the acquisition template we leave the default values.
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: HD 141569. Also, enter the right ascension and declination for HD 141569. 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:
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:
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 IRDIFS OBs in your programme, you type irdifs-cons in the Name field.
Since we want to avoid string variations in the flux seen by the AO wavefront sensor, we enter Clear for the Sky Tranparency conditions.
As for the seeing constraint, you would like to get optimal performance from the AO system have noticed from the user manual that for stars brighter than R=9, reasonable AO performance can be obtained even under moderate seeing conditions. Thus you enter 1.0 in the Seeing field.
The airmass is not a stringent parameter for the irdifs part of your programme, you thus enter 1.5 in the Airmass field.
Lunar Illumination and Moon Angular Distance
The moon has little effect on the SPHERE data quality in the infrared. The default values are hence simply accepted.
The Strehl constraint is currently not considered for observations with SPHERE, so we leave the Strehl at its default value (0.0).
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.
We will assume now that your SPHERE observations are part of a larger multi-wavelength project and that the SPHERE observations should be carried out simultaneously with some satelite observations that are performed between December 01-31 2014. You can specify this, i.e. the execution of your SPHERE OB between December 01 and December 31, 2014 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 2013-12-01T00:00:00.
- In the same way, modify the upper boundary of the time interval to 2012-12-31T23:59:00.
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.
Once the acquisition and the items Target, Constraint 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 SPHERE science templates will appear. Select the template SPHERE_irdifs_obs 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 HD 141569 and the scienctific goal of this OB.
The instrument derotator mode and position angle needs to be identical to the one specified in the acquisition template. So we specify:
Derotator and ADC modes combination: Field
Derotator position angle (deg): 0.0
We would like to use IRDIS for dual-band imaging in the H-band without neutral density filters. Therefore we select:
IRDIS filter combination: DB_H23
Infrared neutral density filter combination: ND_N_0.0
You have used the SPHERE Exposure Time Calculators for IRDIS and IFS to with the setup selected above to determine values for the Detector Integration Time (DIT) at which the detector gets a reasonable number of counts, yet does not saturate:
IFS Detector Integration Time: 8
IRDIS Detector Integratiom Time: 2
We select a reasonable number of DITs per position to limit the overheads associated with jittering:
IFS Number of DIT: 5
IRDIS Number of DIT: 20
We would like to jitter in a 4x4 pattern sequence using IRDIS. As we want to end up with similar execution times in the IFS and IRDIS, and we know that the IRDIS observations, with its smaller DIT, has larger overheads, we set the number of IFS exposures to 20.
IRDIS dithering pattern sequence: 4x4
IFS exposures per dithering position: 20
We also would like to obtain a measurement of the star flux, but as our target is bright, we select a detector integration time of 0, which set the DIT to its smallest possible value (0.83 seconds). We also select a neutral density filter for the star flux measurement:
IFS Integration Time (Flux): 0
IRDIS Integration Time (Flux): 0
Infrared neutral density filter combination: ND_N_2.0
As we are afraid that our object may be large compared to the IFS field-of-view, we also take a short Sky exposure to improve background subtraction for the IFS.:
IFS Number of integrations (sky): 3
IRDIS Number of intergrations (flux): 12
Sky RA offset list (arcsec): 15
Sky Dec offset list (arcsec): 15
The DITs for the Sky exposure are the same ones used for the Object position.
To ensure that we observe one sequence O (Object), S (Sky), F (Flux), we define:
Observation Type (F, C, O, S): O S F
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: HD141569-irdifs
- Status: (P)artiallyDefined
- Target: HD141569
- OD: IRDIFS
- CS: irdifs-cons
- Acquisition: SPHERE_irdifs_acq
- FindingCharts: (0)
You can reshape the columns as indicated in the P2PP User Manual to view the full contents of each entry.
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(S)], which you called 60.A-9253S.hd141569.jpg, and whichis 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-9253S.hd141569.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..
With the completion of the OBs, we consider the examples developed in this tutorial to be finished. The P2PP main GUI displays the OBs which 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(S) 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.
SPHERE P2PP Tutorial
- 0: Goal of the Run
- 1: Getting Started
- 2: Your First OB - Starting with P2PP
- 2.1: Define an irdifs OB with P2PP
- 2.1.1: Filling in the Basic Information
- 2.1.2: Defining the acquisition template
- 2.1.3: Inserting Target Information
- 2.1.4: Setting the Constraint Set
- 2.1.5: Setting the time intervals
- 2.1.6: Setting the Ralibration Requirements
- 2.1.7: Defining the Observation Description
- 2.1.8: Attaching Finding Charts
- 3:Finishing the preparation and submitting the OBs
- 4: Check-Out and removal of tutorial OBs from the ESO Database
- 2.1: Define an irdifs OB with P2PP