Observing schedule preparation

srccat /
    equinox='J2000'
    source='{SOURCE NAME}' ra={hh:mm:ss.ssss} dec={dd:mm:ss.sss} vel={VELOCITY} vref={REFERENCE FRAME} vdef={VELOCITY DEFINITION} /
endcat /

List here all sources that you want to observe and are not available in the standard SCHED (calibrator) catalogs. Include the name, coordinates, and, only in case of spectral line experiments, please add the velocity information of the source (vel=, vref=, vdef=):

• vel: velocity of the source, in km/s, within the vref reference frame.
• vref: reference frame for vel (L = Local Standard of Rest, H = heliocentric, G = geocentric).
• vdef: velocity definition (R = radio definition, O = optical definition).

{SETINI FILE CONTENT}

setup = {SETINI SETUP NAME}  ! For example:  setup = evn6cm-2Gbps-32MHz.set

Please add the general frequency setup for the observation. You will receive this information from JIVE prior to the observation. The setup written here refers to the setups that are stored in ~/.pysched/setup/.

Note that if you use a non-standard setup or you are using the NRAO SCHED program instead of pySCHED, you will need to put explicitly here the full information concerning your setup.

YEAR  = {YEAR}
MONTH = {MONTH}
DAY   = {DAY}
START = {START TIME HH:MM:SS}


optmode = scans

opminel = 9

stations = {LIST OF STATIONS TO BE INCLUDED}

Specify when the observation starts (year, month number, day, and time of the day in UTC format), and the scheduled stations. All this information is available from the EVN Block Schedule.

Antenna names and codes

The antennas that are scheduled for your observation would be quoted in the EVN Block Schedule (you may receive a dedicated email if you are the PI of the scheduled observations). pySCHED does not use the full name of the atennas. Instead, it uses either an abbreviated name of them or the two-letter code that you find in the EVN Block Schedule. In the following we list the correspondence between the full antenna names and the labellings to be used in pySCHED.

Antenna Name	pySCHED name	pySCHED two-letter code
Cambridge	cambg32m	Cm
Effelsberg	eflsberg	Ef
Hartebeesthoek	hart	Hh
Irbene	irbene or irbene16	Ir or Ib
Jodrell Bank (Lovell Telescope)	jodrell1	Jb1
Jodrell Bank (Mark II)	jodrell2	Jb2
Kunming	kunming	Km
Medicina	medicina	Mc
Metsahovi	metsahov	Mh
Noto	noto	Nt
Onsala	onsala85 or onsala60	O8 or O6
Sardinia	sardinia	Sr
Sheshan	shanghai	Sh
KVN Tamna	kvntn	Kt
KVN Ulsan	kvnus	Ku
KVN Yonsei	kvnys	Ky
Tianma	tianma65	T6
Torun	torun	Tr
Urumqi	urumqi	Ur
Westerbork	wstrbork	Wb
Wettzell	wettzell	Wz
Yebes	yebes40m	Ys

7. The Scans

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
! Simple continuum observation

source={FRINGE-FINDER} gap=0:00 dur={5:00} /

source={TARGET} gap={3:00} dur={3:00} /
group 1 rep {X}
	source={TARGET} gap={0:30} dur={14:30} /

source={FRINGE-FINDER} gap={3:00} dur={5:00} /

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
! Phase-referenced continuum observation

source={FRINGE-FINDER} gap=0:00 dur={5:00} /

source={PHASE-CALIBRATOR} gap={3:00} dur={2:00} /
group 4 rep {X}
	source={TARGET} gap={0:00} dur={3:00} /
	source={PHASE-CALIBRATOR} gap={0:00} dur={2:00} /
	source={TARGET} gap={0:00} dur={3:00} /
	source={PHASE-CALIBRATOR} gap={0:30} dur={1:30} /

source={FRINGE-FINDER} gap={3:00} dur={5:00} /

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
! Phase-referenced  spectral-line observation

source={FRINGE-FINDER} gap={0:00} dur={5:00} dopsrc={TARGET NAME} /

source={PHASE-CALIBRATOR} gap={3:00} dur={2:00} dopsrc={TARGET NAME} /
group 4 rep {X}
	source={TARGET} gap={0:00} dur={3:00} dopsrc={TARGET NAME} /
	source={PHASE-CALIBRATOR} gap={0:00} dur={2:00} dopsrc={TARGET NAME} /
	source={TARGET} gap={0:00} dur={3:00} dopsrc={TARGET NAME} /
	source={PHASE-CALIBRATOR} gap={0:30} dur={1:30} dopsrc={TARGET NAME} /

source={FRINGE-FINDER} gap={3:00} dur={5:00} dopsrc={TARGET NAME} /

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
! Polarization observation

source={FRINGE-FINDER} gap=0:00 dur={5:00} /

! EVPA
! Every 1 hour
source={POLARIZATION-CALIBRATOR} gap={0:00} dur={5:00} /

source={PHASE-CALIBRATOR} gap={3:00} dur={2:00} /
group 4 rep {X}
	source={TARGET} gap={0:00} dur={3:30} /
	source={PHASE-CALIBRATOR} gap={0:00} dur={2:00} /
	source={TARGET} gap={0:00} dur={3:30} /
	source={PHASE-CALIBRATOR} gap={0:30} dur={2:00} /

source={POLARIZATION-CALIBRATOR} gap={0:00} dur={5:00} /

source={FRINGE-FINDER} gap={3:00} dur={5:00} /

8. Output SUM file

SCHED/PySCHED produce different output files. You may want to look at the .sum file to verify the schedule of your observation.
The example below shows the scan summary section included in the output of the created .sum file for a given experiment using sumitem = el1, early.



This is a summary of all scans that will be observed in the observation, with the relevant data (indicated in the sumitem command) for each station (columns). In this example, the first row of each scan shows the elevation of the source at the start of the scan. The second row quotes the number of seconds that a station is on source before the start of the scan. Negative values show for how long the antenna is still moving from the previous source position until it reaches the current one.
For System Temperature measurements, the values from the second row should be at least 10 seconds every 10-13 min for all antennas with non-coninuous Tsys measurements (see System Temperature Measurements section).

Things to consider

dwell parameter

The dwell parameter is an alternative way to specify the duration of a scan. The difference to dur is that the start time of the scan is delayed until all antennas are on-source (taking into account the slewing and settle time of each antenna). This implies that telescopes will be idle waiting for the slowest antenna to reach the source position instead of recording once they individually reach the source. For EVN observations this must not be used since the different telescopes of the EVN have significantly different slewing times, and thus a significant loss of on-source time can be encountered. In addition, due to the flexibility of the EVN (specially in the e-EVN mode) some antennas may be added in the last minute, producing that the full schedule would change if dwell is in use. Therefore, please always use the parameter dur instead.

System Temperature Measurements

The EVN telescopes regularly measure system temperatures using noise diodes. Some telescopes can measure the temperatures continuously. However, the other stations measure them only when there are long enough time gaps between observing scans. This refers to time gaps that guarantee at least 11 seconds on source for these stations at the beginning of the scan. One of these long gaps must be scheduled every ~10-13 minutes (SCHED/PySCHED will provide warnings for intervals between gaps of more than 15 minutes). You can check the length of time gaps by looking at the .sum output file (see Output section) using the early attribute in sumitem (see Program Control section).

Effelsberg Pointing

Effelsberg is a 100-m antenna that requires periodic pointing scans. To achieve a good pointing precision, Effelsberg has to have an eight-minute period without recording every four hours (for 6, 5, and 3.6 cm; i.e. C, M, and X band), and every two hours (for 1.3 and 0.7 cm; i.e. K and Q band). No pointing scans are required for 21 cm (L band) or longer wavelengths. This eight-minute period can be achieved by either having a gap of eight minutes in the schedule or taking Effelsberg out of the station list for some scans.

Jodrell Bank (Lovell Telescope) slewing limitations

The Lovell Telescope (typically known as Jodrell1, or Jb1, in EVN schedules) has a slewing limitation of 12 source-changes per hour (which is equivalent to a ten-minute cycle time between two sources). If you want to go to a faster cycle time and/or are using a traditional phase-referencing cycle like the one quoted above, it is required to schedule an observing pattern that omits the Lovell Telescope every other reference-source scan.
A convenient way to perform this is illustrated in the following phase-referencing example:

group 4 rep {X}
    stations = jodrell1, all other antennas 
    source={TARGET} gap={0:00} dur={3:00} /
    source={PHASE-CALIBRATOR} gap={0:00} dur={2:00} /
    source={TARGET} gap={0:00} dur={3:00} /
    stations = all other antennas     ! NOTE THE LACK OF jodrell1 
    source={PHASE-CALIBRATOR} gap={0:30} dur={1:30} /

stations = jodrell1, all other antennas ! Continue with the full array
    

In this way, the Lovell Telescope (Jodrell1) will not observe every other scan on the phase calibrator. Instead it will keep observing the target source.

Required calibrator sources

A regular VLBI observation requires to observe different calibrator sources in order to properly calibrate the data. Depending on the science and observational case, multiple strategies and sources may be desired. In a general case, we require to observe:

• At least two scans during the observation on a very bright and compact source (fringe-finder). These data will be used to clock search the full observation (synchronize the data from all antennas in time), and they can be used during the data reduction to perform the bandpass correction and the single-band delay calibration (see our EVN Data Reduction Guide and EVN Tutorials for further information). This source does not require to be near your target source (although nearer would imply less slewing time for the antennas when moving from one source to another). But all antennas must be observing some of the fringe-finder scans.
• Phase-referencing calibrator source. Unless the target is very bright, compact, and no absolute astrometry information is required from the data, the target source must be observed following a phase-referencing strategy (see sections above). A nearby calibrator source needs to be observed regularly in order to properly calibrate the data and transfer these solutions to the target source data. You can see our section on calibrator selection to pick a good calibrator source.
• If polarization information is required from the observation, a polarization calibrator is required to be observed. See the section above on polarization observations for further details.
• If the e-MERLIN antennas are observing, we recommend to observe at least one scan on 3C286, the amplitude calibrator for this array. This source will help you to better calibrate the amplitudes (gains) of each of these antennas by following their usual calibration approach with a model of the source. This can be used during EVN observations by applying this strategy to only the e-MERLIN antennas.

To-Do list for schedule checking

The following list can be used as last step before sending your schedule file to the EVN to verify that all information is correct. It goes through the main points that could go unawarely wrong. In any case, note that the EVN User Support will also verify your schedule before observations.

1. Verify that the experiment code in EXPCODE is the correct one (including epoch letter if needed; e.g. EA123A).
2. The date and UT range (start and end time) must match the allocated block schedule.
3. Set a lower-limit elevation for antennas (right after the start date/time of the observations at the beginning of the scan section):
   
optmode=scans

opminel=7 or 9
4. Targets sources
   1. Targets approved by the PC for the particular epoch.
   2. Verify that the coordinates are the correct ones for the target.
5. Frequency setup. Check that the loaded setup is the correct one.
6. Check that the scheduled stations are the ones in the block schedule.
   
Note differences between On60/On85, Ir/Ib, or Jb1/Jb2 antennas.
7. Gaps in the scheduled scans (Tsys measurements, and pointing).
   1. Antennas without continuous system-temperature (Tsys) calibration require to have a 'gap' at least every 10–15 min for Tsys measurements. 
The most up-to-date table with the continuous calibrations at stations is in the MPI Wiki.
 Although this information can also be seen in the .sum output file (see section above).
   2. Effelsberg requires a 8-min gap for pointing every four hours at C band (5 GHz) and above, and every two hours at K and Q band (20 and 40 GHz, respectively).
   3. Always use gaps larger than 11s to avoid problems encountered earlier with how field-system interprets minimum gap-length at some stations.
8. All stations should always be observing at least two scans on fringe-finders during the observation. If the observation is long (e.g. >5 h) then more fringe-finder scans is desirable.
9. Sources and Scans:
   1. Certify that the phase-referencing calibrator (if any) is bright and compact enough.
   2. The phase-referencing calibrator must be close to the target source.
   3. All sources are far from the Sun (check the .sum file).
10. For spectral line experiments.
    1. Make sure that targets and their calibrators (phase-referencing, bandpass, etc.) use the same DOPSRC source.
    2. If possible, check the VEL/VDEF/VREF parameters that control the Doppler calculation, especially with narrow subband-BW.
11. For polarization experiments, suitable calibrators (D-term and EVPA) should be observed.
12. For eMERLIN antennas, if they are included, schedule an amplitude calibrator (3C286) for them.