Information for Astronomers
Information for Astronomers
Since July 2010 a new antenna control and observing software is used at the Effelsberg 100m telescope. The interface for the observer is called "OBSINP". It allows the control of all observing modes possible at the Effelsberg antenna. This document gives a brief introduction to all the different sections in OBSINP for each observing mode. More details on how to set up and organize observations of different types are given in the individual sections of the User Guide.
All observations are stored and organized by a queue system that allows to prepare the next steps during your current observations are in progress. It also allow to prepare observations in advance for later processing at the telescope. The structure of the program is shown in Fig. 1.
The buttons on the top are controlling the processing of telescope queue. The Start button will start the observations in the current queue. The Stop button will stop the observations. If the antenna stops for some reason or the observations are stopped by the user the current scan can be repeated from the beginning by pressing Repeat. Continue will continue the current scan at the sub-scan where the antenna was stopped. Pressing Start will abort the stopped scan and continue with the next scan in the queue.
On the left side the observer can choose from various menus on different topics that are mainly structured in a way that they guide through the observations. The general setup is made at the beginning including frontend and backend settings. The SetupCont menu contains windows for pointing and focus that every observation should start with and the other modes like spectroscopy, Pulsar and VLBI follow.
In detail there are:
SetupVLBI (See VLBI-Handbuch):
The buttons at the bottom have the following functions:
The General Menu has to sub topics Control and Startup. In the Control widget (Fig. 2) the observer can send commands directly to the telescope control software (take care! you have to know what you do). The syntax for this is written down elsewhere. It is possible to prepare configuration files that can be load by typing '@config-file'.
At the bottom the active queue can be selected. The "normal" queue for the observer is the UserQueue, but if e.g. the operator has to test something in between or the observer wants to insert a scan without changing his current queue, the active queue can be change to the OperatorsQueue and filled with alternative scans, be observed, and changed back to the UserQueue for further observations.
The Startup widget is the first screen that appears when you call OBSINP and should be filled with the information that is requested: Operator, Observer, Project-Code, and the working directory. The observers directory will contain the folders for his own catalogues and scripts. The directories are called Catalogues and Scripts and will be created by the system if not already existing.
The preparation of scripts is described later in the Pointing and Spectroscopy sections.
With the new Obsinp observing software, source catalog files are stored in the SDB (structured data base) format. This format is somewhat less easy
to understand as the (old) VAX source catalogs. However, there exists a script
catalog.py, which can be used to convert files having the old VAX format to the new Obsinp format. Using
on the observer2 computer will create a file
sources.sdb. If you place it into
/home/obseff/your_obs_directory/Catalogues it will be found automatically by Obsinp (if you choose the correct startup directory).
For the preparation of your observations we recommend to prepare a catalog in the VAX format and convert it into the new format afterwards.
Alternatively, you might use our catalog tool for creating and editing catalogs, see pycatalog.
The ScanList shows the most recent 100 scans with some basic information about observing modes and receivers used (Fig. 3, top).
Figure 3: Top: The ScanList shows the most recent 100 scans with some basic information about observing modes and receivers used. Bottom: Example for a queue filled with pointing scans using different secondary focus receivers.
The Telescope_queue (or Queue Manager) displays the current queue and allows to shift and delete scans from the queue (Fig. 3, bottom). The current UserQueue is written as single files for each action in the /home/obseff/.SYSTEM/Queue/User directory. To prepare observations in advance or save queues for repeated observations like monitoring it is possible to save the queue-files or directory at some other place and restored it later again. For example you can write the files in a compressed tar-archive: change into the UserQueue directory and run "tar -czf ../../<dir-name>/todays_queue.tar.gz *" to save all files into your directory in todays_queue.tar.gz. "tar -xzf todays_queue.tar.gz" will extract the files in the current directory.
The Frontends entry in the widget selection contains two menus for the selection of secondary and primary focus receivers. Each receiver has different versions. For most continuum observations the Continuum BroadBand (BB) version is the best choice, since it provides the maximum band width. For Pulsar observers the pulsar versions and for spectroscopy observations one of the line version should be chosen:
There is no default version, the observer must select one. Not all receivers provide both IFs. Frequency and side band have defaults that should be fine for most continuum observers. For spectroscopy the correct line frequency has to be given, the side band selection is done automatically. A manual side band selection is not recommended. More details about the receiver versions can be found here (in progress) and the receiver capabilities are described here.
The Frequency menu allows the selection of lines by name from a line catalogue or the direct input of a frequency in GHz. You can add private line catalogues to your Catalogues directory. The catalogue should have the extension .lin. The format is
Line-Name - Frequency in GHz, e.g.
Please note, that some receiver have different versions for different frequency ranges. E.g. the 1.3cm prime focus receiver has two version from 18 to 22 GHz and from 22 to 26 GHz. Take care that the correct version was loaded before changing the frequency from the Frequency menu.
For the continuum backend Beacon there are currently no options. From the two menus for the FFT Spectrometers (XFFTS and AFFTS) the IF channel, the number of channels, and the filter (total band width) can be selected.
Every observing session should start with a sequence of pointing, focus, and pointing observations to verify that the system is working properly. Bright suitable sources are displayed on the AstroPC in the control room. Many of the primary flux density calibrators are suitable for that and can be directly used for calibration. For spectroscopy it is also recommended to observe a known line source to verify the proper functionality of the FFTS (see Spectroscopy). Continuum data as cross-scans and maps can be viewed offline and reduced using the Toolbox
After completion of the focus scan the active queue will be stopped and the antenna is waiting for new input. If the fit was successful the focus correction will now appear in the Offsets: Focus_offset menu at the bottom of the left widget list in the ZLinear field. If the fit failed or the value needs to be corrected by hand for some reason this can be done here as well. Pressing Load to telescope queue will load the corrections to the first position in the queue independent of how many other scans are in the queue already. The antenna will continue observing with the new corrections after the Start button is pressed. When the focus corrections are not applied manually, pressing the Start button will continue the observations without using any focus corrections.
The Mapping menue allows to cover a defined area around a given position of an (extended) radio source with many divers options. Usually, the position of the source is taken as the reference point (but not necessarily the map centre) with the parameters ObjectName and its coordinates given in the coordinate system chosen by CoordinatSystem, Equinox, and Projection (either Cartesian or as Sanson-Flamsted (SFL)), with the corresponding coordinates written in ObjectLongitude in [hh.mm.ss] and ObjectLatitude in [d.'."]. Instead of typing in the coordinates you can automatically select them from a source catalog chosen in Catalog where you also can access one of your private catalogs. For observations with multihorn receivers you should always scan along azimut so that all horns will cover the source subsequently. Therefore please choose Azimth/Elevation in Scanning_in. In this case it doesn't matter what you choose in CoordinateSystem and SCANDirection.
If you wish to get a rectangular map of your source (which is the standard way), please choose UserSystem=Descriptive. The option Absolute will give the map in absolute coordinates. A few recommendations how to set up maps for different receiver systems are given here.
The coverage usually starts at the lower left corner of the map, scanning either along Longitude or Latitude as chosen in SCANDirection. With the parameter SCANSpacing you choose the distance of the next subscan of your map above the first one along which the telescope drives backwards. The telescope's beam will cover the total map with this SCANSpacing forwards and backwards (if you choose ZigZag= True) with a velocity given by SCANVelocity (give [unit]/sec, i.e. 30" means 30 "/sec starting with the SubSCANStart (which is 1 if you start the map from the beginning). Notice, that you need e.g. 21 subscans for a mapsize of 30'x20' (with SCANDirection=Longitude) if your SCANSpacing is 1'. With SCANRepeat you choose how often you repeat one subscan, it is usually set to 1.
The total map extent is given in ExtensionLongitude and ExtensionLatitude. Please give the units explicitely, either in ", ', or deg, no unit means by default degrees. You may also define an offset of the map center relative to the source position in longitude with LonOff and in latitude with LatOff which is necessary for multibeam observations. With ScanRotation the total map can be rotated relative to the chosen coordinate system, positive value means anticlockwise rotation, starting at north.
There are two other options if you don't like to start observing your map in the lower left corner: if you choose the SCANVelocity negative, the telescope starts the first subscan driving along minus longitude, with a negative value for SCANSpacing it goes down (instead of up) from one subscan to the next one. Hence, if you choose both parameters negative, the telescope starts at the upper right corner of the map.
With the option Load to Telescope queue you can add this specific mapping menu to the end of the telescope queue.
The Pointing menu allows to customize the cross-scans parameters and load scans into the active queue. The Defaults button will reset all parameters. If you are new to the system and don't know what kind of observations were done before it is wise to press default to reset unwanted source position offsets or special features that are not generally used. The template has the following fields (see Fig. 5):
A successful search will fill the ObjectLon. and ObjectLat. fields with the correct values and will set the CoordinateSystem and Equinox as given in the catalogue. The new catalogue format is somewhat cryptic and therefore it is recommended to just convert your old VAX-catalogues using the program "catalog.py". A new catalogue preparation tool is planed.
The Scanning_in, SCANDirection, -Rotation, -Length, -Time, and -Repeats options are more or less self-explanatory, but to be save:
Table 1: Meaning of different numbers in POINTcorr.
|-1||no corrections applied, queue is continued without interruption|
|0||no corrections applied, queue is halted. Observer needs to decide whether he wants to correct manually using the Pointing_Offset menu|
|1||corrections are applied automatically, if amount is less than one beam|
|2||corrections are applied automatically, if amount is less than two beams|
|…||continues like this but doesn't make much sense|
A completely filled form is shown in Figure 6. Pressing load to telescope queue will send the pointing scan to the queue and more scans can be added. The Start button will start the queue and more scans can be loaded while the antenna is running. If the queue is ones empty and new scans are added the Start button has to be pressed again to continue observing. If the antenna stops for some reason or the observations are stopped by the user the current scan can be repeated from the beginning by pressing Repeat. Continue will continue the current scan at the sub-scan where the antenna was stopped. Pressing Start will abort the stopped scan and continue with the next scan in the queue.
The SaveScript button will save the current pointing parameters into a file called "Pointing" in your Scripts directory. This can be used to reload the parameters at a later time again. Such scripts are called from the Pointing menu by typing "@Pointing" in ObjectName and press Search. All fields will be filled with the parameters found in the script. Pressing load to telescope queue will send the new scan to the queue. Such saved scripts can also be used as templates to make new scripts by "hand", but most parameters does not need to be changed so one can also reduce the scripts to the parameters that might change from scan to scan. All parameters need to be separated by a ";" and the parameter from its values is separated by a blank. E.g. to simply load two scans at a time to the queue use the following script:
3C286 ; POINTcorr 1 ; SCANRepeats 2 ; SCANTime 25 ; TopoMode AUTO ; Catalog Default 3C286 ; POINTcorr 1 ; SCANRepeats 2 ; SCANTime 25 ; TopoMode AUTO
To load more different scans on different sources, parameters can be changed. The source needs to be always at the first position other parameters don't need to be in some order.
3C286 ; POINTcorr 1 ; SCANRepeats 2 ; SCANTime 25 ; TopoMode AUTO 3C147 ; SCANTime 25 ; POINTcorr 1 ; SCANRepeats 2 ; TopoMode AUTO
If no parameters change you only need to note them once and the following scans will be done with the same settings. E.g.
3C286 ; POINTcorr 1 ; SCANRepeats 2 ; SCANTime 25 ; TopoMode AUTO 3C48 3C147
More useful might be scripts without a source name at the beginning. E.g., if you prepare a script called "cal2":
; POINTcorr 1 ; SCANRepeats 2 ; SCANTime 25 ; TopoMode AUTO ; POINTcorr 1 ; SCANRepeats 2 ; SCANTime 25 ; TopoMode AUTO
it can be used to do two cross-scans after each other just by typing "@cal2:3C286" or "@cal2:3C48" to make two cross-scan on that source.
With the "FE:" key one can also select different secondary focus receivers to be loaded automatically. Versions are controlled by the "VERn" option and frequencies can be changed by the "Frequency" key. A script for all receivers looks like this:
# # 2.8cm Continuum narrow band (BW 300MHz) + Polarimeter, beam switch # FE:S28mm ; POINTcorr 1 ; SCANLength -4 ; SCANRepeats 2 ; SCANTime 25 ; POINTcorr 1 ; SCANLength -4 ; SCANRepeats 2 ; SCANTime 25 # # 9mm Continuum broad band (BW 4 GHz), beam switch # FE:S9mm ; VERn 2; Horn 5 ; POINTcorr 1 ; SCANLength -4.5 ; SCANRepeats 2 ; SCANTime 25 ; POINTcorr 1 ; SCANLength -4.5 ; SCANRepeats 4 ; SCANTime 25 # # 2cm Continuum broad band (BW 2 GHz) + VLBA Polarimeter # FE:S20mm ; VERn 3 ; POINTcorr 1 ; SCANLength -4.5 ; SCANRepeats 2 ; SCANTime 25 ; POINTcorr 1 ; SCANLength -4.5 ; SCANRepeats 2 ; SCANTime 25 # # 7mm LSB Continuum broad band (BW 2 GHz), LCP at 42.9 GHz # FE:S7mm ; POINTcorr 1 ; SCANLength -4.5 ; SCANRepeats 4 ; SCANTime 25 ; POINTcorr 1 ; SCANLength -4.5 ; SCANRepeats 4 ; SCANTime 25 # # 1.3cm Continuum broad band (BW 2 GHz) + VLBA Polarimeter # FE:S13mm ; VERn 3 ; POINTcorr 1 ; SCANLength -4.5 ; SCANRepeats 2 ; SCANTime 25 ; POINTcorr 1 ; SCANLength -4.5 ; SCANRepeats 4 ; SCANTime 25 # # 3.6cm Continuum broad band (BW 1.1 GHz) + Polarimeter # FE:S36mm ; POINTcorr 1 ; SCANLength -4.5 ; SCANRepeats 2 ; SCANTime 25 ; POINTcorr 1 ; SCANLength -4.5 ; SCANRepeats 2 ; SCANTime 25 # # 6cm Continuum broad band (BW 500 MHz) + Polarimeter, beam switch # FE:S60mm ; POINTcorr 1 ; SCANLength -4 ; SCANRepeats 2 ; SCANTime 25 # # 11cm Continuum narrow band (BW 80 MHz) + 8K Polarimeter # FE:S110mm ; POINTcorr -1 ; SCANLength -4.5 ; SCANRepeats 2 ; SCANTime 25
Saved as "all" such a script can be again combined in another script to observe a number of sources at all available receivers. E.g. a script called "go_poi" might contain
#Calibrator at all SFK RX @all:NGC7027 #Target source at all freq @all:3C454.3 #Target source at all freq @all:bllac #Target source at low freq only @low:2318+049 # Again a calibrator @all:NGC7027
Lines starting with "#" denote comments. This script will measure first NGC7027 at all secondary focus receivers and then 3C454.3 and BLLac. 2318+049 is only observed at the lower frequencies and NGC7027 again at all. Such a script will run for about 2.5 hours.
Figure 7: It is possible to load scripts that perform several pointings. To load a script into the queue type "@script" (if the source is in the script) or "@script:source" (if the source field is free) in ObjectName, then press Search and load to telescope queue.
Every observing session should start with a sequence of pointing, focus, and pointing observations to verify that the system is working properly. Bright suitable sources are displayed on the AstroPC in the control room. Many of the primary flux density calibrators are suitable for that and can be directly used for calibration. For spectroscopy it is also recommended to observe a known line source to verify the proper functionality of the FFTS.
Currently, there are two basic measurement schemes implemented, i.e., position and frequency switching. In position switching, one defines a so-called reference (REF) position which is used to remove the bandpass from the On-source (ON) spectrum. In frequency switching the reference spectrum is obtained by using a slightly different local oscillator (LO) frequency. For more information on these methods we refer to (insert link here).
Of course the above methods are more or less independent on the astronomical observing mode, i.e. a pointed observation or a mapping (either in a Raster or On-the-fly). In order to have a pointed observation, one just chooses from SetupSpec:
Figures 8 and 9 show the associated input masks, which the user has to fill. The fields have the following meaning
As mentioned before, the Raster can either be done using Position or Frequency switching. Consequently, after defining the map using the input fields below, one has to either push the FSwitch or PSwitch Button. Obsinp will then bring up the correct input form (see Fig. 8 and 9) such that the user can choose the switching-specific values.
Using 45 degrees the raster can be more densely packed (if SCANYSPC is choosen accordingly smaller):
Again OTF can either be done using Position or Frequency switching. Consequently, after defining the map using the input fields below, one has to either push the FSwitch or PSwitch Button. Obsinp will then bring up the correct input form (see Fig. 8 and 9) such that the user can choose the switching-specific values.
Note, that ExtensionLongitude/ExtensionLatitude together with the SCANVelocity defines the integration time per subscan. Hence, the input field in the PSwitch/FSwitch is redundant and not used.
In the PSwitch and FSwitch forms, one can use the SaveScript Button to automatically create a Macro (or Script) file in the current working directory (as set in the StartUp form). These Macros initially get a standard name (e.g., FSwitch, FRaster, POnTheFly, etc.). Consequently, one might want to rename these files for later use. If one first setups a map and pushes the SaveScript Button in the following PSwitch/FSwitch form, the mapping parameters are also contained in the Script file. One can easily change the Parameters in the Scripts, use different sources/catalogs, etc. One can also start scripts within scripts using the "@scriptname" syntax.
To start a script one types in "@scriptname" into the ObjectName field. One can even override the source with another source (from the same catalog!) using the colon-feature: "@scriptname:anothersource". If the script contains several subscripts (e.g. several Raster maps), then all of them will be added to the queue.
A list of scripts for PSwitch tests for different receivers is given in the table below. The directory in the Startup Menu has to be set to /home/obseff and then you can just type "@<script-name>" in the ObjectName field in the SetupSpec: PSwitch menu, press Search, "load to telescope queue" and Start.
|Prime focus receivers|
|RX||Version||Script name||Frequency [GHz]||Source||FFTS (IF/Filter)||Comment|
|P300mm||1||30cmLine||1.139||1413+135||150/20||30cm PFK, 1413+135 not circum-polar absorption line|
|P300mm||1||rrlP300mm||1.281||W3Main||150/20||30cm PFK, recombination line H172alpha|
|P200mm||2||18cmpol||1.665||W3OH||150/20||18cm PFK,polarization test (LCP, RCP profile differ)|
|P90mm||2||rrlP90mm||3.408||W3Main||150/20||9cm PFK, recombination line H124alpha|
|P50mm||1||rrlP50mm||6.107||W3MAIN||150/100||5cm PFK, recombination line H102alpha|
|P50mm||1||maser5cm||6.669||W3OH||150/20||5cm PFK, methanol maser|
|P22mm||1||rrlP22mm1||12.149||W3MAIN||150/100||2.5cm PFK, recombination line H81alpha|
|P22mm||2||rrlP22mm2||13.089||W3MAIN||150/100||2.2cm PFK, recombination line H79alpha|
|P19mm||1||oh1.9cm||13.505||W3OH||750/100||1.9cm PFK, OH line|
|P19mm||2||rrlP19mm||17.992||W3MAIN||750/100||1.9cm PFK, recombination line H71alpha|
|P13mm||1||rrlP13mm1||20.462||W3MAIN||750/100||1.3cm PFK, low band, recombination line H68alpha|
|P13mm||2||rrlP13mm2||23.404||W3MAIN||750/100||1.3cm PFK, high band, recombination line H65alpha|
|P13mm||1||wasser||22.235||W3OH||750/100||1.3cm PFK low band, water maser (very strong, not a good test source)|
|P10mm||2||1cmtest||30.002||W3(H2O)||750/100||1cm PFK, middle band, SO line (?)|
|P10mm||1||rrlP10mm1||28.275||W3MAIN||750/100||1cm PFK, lower RX band, recombination line H61alpha|
|P10mm||2||rrlP10mm2||29.700||W3MAIN||750/100||1cm PFK, middle RX band, recombination line H60alpha|
|P10mm||3||rrlP10mm3||34.596||W3MAIN||750/100||1cm PFK, upper RX band, recombination line H57alpha|
|P6mm||1||maser7mm||43.122||R Cas||750/20||6.5mm PFK, SiO maser, circum-pol. but passes hills and zenith|
|P3mm||1||maser3mm||86.243||R Cas||750/20||3mm PFK, SiO maser, circum-pol. but passes hills and zenith|
|Secondary focus receivers|
|RX||Version||Script name||Frequency [GHz]||Source||FFTS (IF/Filter)||Comment|
|S100mm||1||rrlS110mm||2.703||W3MAIN||150/20||11cm SFK, recombination line H134alpha|
|S60mm||4||rrlS60mm||4.874||W3MAIN||750/100||6cm SFK, recombination line H110alpha|
|S36mm||3||rrlS36mm||8.585||W3MAIN||750/100||3.6cm SFK, recombination line H91alpha|
|S28mm||1||rrlS28mm||10.522||W3MAIN||150/100||2.8cm SFK, recombination line H85alpha|
|S20mm||3||rrlS20mm||14.690||W3MAIN||750/100||2.8cm SFK, recombination line H76alpha|
|S13mm||3||rrlS13mm||23.404||W3MAIN||750/100||1.3cm SFK, recombination line H65alpha|
|S7mm||1||maser7mm2||43.122||R Cas||750/20||7mm SFK, SiO maser, circum-pol. but passes hills and zenith|
As an example of wath the scripts are doing: rrlP13mmh
# 1.3cm PFK high band test line # 23.4 GHz - H65alpha Übergang von Wasserstoff # FE:P13mm; VERn 2; Frequency 23.40428 W3MAIN ; SCANTime 60 ; RefOffsetLon 1800" ; RefOffsetLat 0 ; SCANRepeats 1 ; NRepeats 1 ; RefPosition_in Azimuth/Elevation ; SourceVelocity -44 ; VMode Corrected(Sub) ; VelSystem VLSR ; Catalog alex
If no test line for your receiver is given in the table and no source is known, it is likely that a Radio Recombination Line of Hydrogen is close to your target frequency (see the Spectral Line folder in the control room) that is observable on W3MAIN. The observable RR-Lines are listed in the RRL line catalogue. The right frequency has to be selected together with the receiver from the Frontend Menu. The position of W3MAIN is in the default source catalogue.
Please ask local staff or the pulsar group in Bonn for more information.