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The following procedures are given to cover most situations.
All checks and changes to the operating procedure should be noted,
in particular anything that might alter the observations, as well
as a summary of any results of tests made. Breakdowns should
not only be noted, they should also be reported to the head of
I&C (who is responsible for the system) and the head of the
reduction group (who is responsible for observations).
Times can be given either in local time MET or in universal time
UT. Whenever there is mention of a time it is normal to quote the
UT time, but this should be stated explicitly in the logs and
on chart recorders. Similarly dates are normally given as UT day numbers
(=day of year, so that 1 Jan=day 1), although it is convenient to note the
civil date as well in the log book.
The general items to log are the following:
- The weather (temperature, humidity, wind).
-
The weather affects the observations, because of refraction and extinction
effects and a high wind can affect the pointing
- The pointing of the telescope.
-
The telescope pointing (difference between computer and hardware readout)
must be checked once a (work)day. See `Checking current observing status'
- The clock offset.
-
See `Checking the clocks'.
- The total power levels of the telescope, particularly signs of
-
interference.
See `Checking total power levels'
- Any error messages.
-
Error messages from the correlator will appear on the system console,
whereas error messages from the schedule will appear on the terminal
where the schedule is running. Log both types in the logbook, and
the schedule error messages in the listing of the schedule.
A message from the observation of :
MEASUREMENT STOPPED, POINT AGAIN
just means that the telescope could not reach that source at the expected
time, and the rest of the schedule proceeds as normal. Such messages
should be noted.
- Check the current time on the UT clock
- Check the schedule. Use the command:
RU,STATE
to see what is actually being observed now.
- Check in the appropriate part of the observing schedule listing
if the current observation agrees with what the telescope should be observing,
within the time margins noted in the schedule.
If not inform the system group of the problem immediately
- Check the telescope pointing.
- Wait for the telescope to stop moving (during a gap between
observations).
- Use the program
TTEL to read the computer's version
of azimuth and elevation (options 'read' and 'both'), and compare
these with the hardware readout in the centre of the racks. If these differ
by more than 0.05degrees, and there is not a storm, warn the system group
and note the discrepancy in the logbook. If the value is
less than 0.05degrees, just note it in the logbook.
- Check the total power (see below).
- Check the weather (temperature and windspeed). Note the
temperature and windspeed (if over 20km/s) in the logbook.
The instantaneous total power can be checked on a counter (to
the left hand side of the rack). With the current settings the
total power readout there is approximately 10 times the system temperature,
so that for a cold area of sky and our current system temperature the
readout should be about 350-450 units.
The total power is also recorded for 2 of the IF channels on two pens
of the chart recorder (in rack on right hand side). These traces should be
stable except when:
- The noise source turns on (a step up for a short period).
- Interference (EMI) occurs. This gives an irregular total power
recording for a time, and later (we hope) returns to normal.
This can be seen as irregular jumps in the total power levels.
- A strong source is seen. This should normally only
correspond to times when a strong source (e.g. a calibrator
See section Calibration Sources) was scheduled. The change in total power
is fairly steep going on source or off source, but the total power should
remain stable (except for the noise tube turning on) while onsource.
- The gain of the receiver drops, or the receiver switches frequency.
This can be seen as an overall drop in the total power level, which is
stable and non-zero, and noise source steps can still be seen.
- The receiver stops working. In this case the total power
drops to zero on both traces and stays at zero.
There is a special program, TSYS, to calculate the system temperature
and noise tube values from measurements of strong calibration sources
See section Calibration Sources.
The input comes from total power values from the output listing of
a measurement of such a system temperature measurement, so before
running the program:
- Make sure you have run such an observation.
Currently there are standard observation files `NT21C' (short) and
`LA21T' (long) for 21cm calibration.
- Run the program GARED (bit option 2) to give total power values on
the output listing.
Run the program TSYS, which asks for the following items:
- Total power on the calibrator (2 values, separated by a comma)
(one value per IF channel)
- Total power off the calibrator (2 values, separated by a comma)
(one value per IF channel)
- Estimated noise source value (`TCAL')
- Source number (a code for which calibrator was used:
- Cas A
- Cyg A
- Tau A
- Vir A
For Cas A a date is also requested in the form `yyyy,ddd'
- Frequency (MHz)
- Total power, and Gain observed on the North Pole
The program will then calculate system temperatures and noise source values.
Note these in the logbook
- Check the computer clock is (approximately) at the correct time
with the command
TI. This reports year,day number,hours,minutes,seconds.
The time should be the local (MET) within an accuracy of 15minutes.
If it is not, use the TM command to set the computer clock.
- Check the DCF-77 Clock. This is the MET time, and has an accuracy
better than 1millisecond.
- Check the UT clock time (the panel under unit
W103-Z)
against the DCF-77 clock time; after correcting
for the 1 or 2 hour time difference (winter and summer time respectively)
the UT clock must have the correct time to within 1 second.
If it UT clock has an error more than 1 second:
- Note the error
- Stop the schedule (if the error is more than 3seconds)
or wait unit a gap in the schedule (if the error is less than 3seconds).
- Re-set the clock
- Note the (corrected) time that the clock was re-set
- Restart the schedule if necessary
- Write down the error and when the clock was re-set in the
logbook and listing of the schedule.
The MET time is always later than the UT time. If you are not sure
tune the radio to the BBC world service where news bulletins give the
Greenwich Mean Time (GMT is the same as UTC).
For a small change (less than 3 seconds)
- Turn the key to the lock directly under the UT display
on the unit, so that it is in the 'in' position.
- With the last 3 digits of the thumbwheel at 999 (=999milliseconds)
chose the sign for the modification (on thumbwheel) and press the
button immediately to the right of the key switch.
- Check the clock display. If more than 1 second needs to be changed,
repeat the previous step.
If more than 3 seconds needs to be changed, you may prefer to reset the
whole clock, using the SET button to modify the value of the digit
chosen by the lefthand thumbwheel digit.
- Turn the switch (2nd on right of key) to the position `T'.
At this point the time in degrees stops.
- Choose a digit to modify, using lefthand thumbwheel to give
the number of the digit in the display.
- Use the
SET and RESET buttons to change this digit.
- Set the 'time in degrees' by modifying it, as in the previous step
but with the switch (2nd on right of key) to the position `T0'.
Set the value to be slightly ahead of the actual time in degrees.
When the value is correct the display will be
updated. The value is automatically reset at 00:00:00UT.
- Put the switch the 2nd on right of key to the central position `-'.
- Rotate the key to the out position
At the year change there may be a problem with the year number
as stored in the information file `INFOFL'.
Change the value of the year in this file with the program INFFL
as soon as practical after the new year.
The Synthesizer used is the Schomandl under the Synthesizer Control
Unit (W271).
The procedure is
- Make sure that no observations are running.
- Run TESSY
- Set a frequency
- Read back the frequency.
Note that the system does not
read back the Schomandl synthesizer setting, only
the value that the control unit has. This should correspond to the value
shown on the control unit's display.
There is a program TLINK which performs this test,
(no documentation!). The program sets indiviual bits, and reads them back
to see whether they are sent correctly.
Run the program DWTST, as described in Note 545.
After an observing schedule has finished, the observations made
will be listed to the line printer. When this has finished, you
may choose some scans to be examined, e.g. because the spectrum is
known and so can be checked, or because there is interference suspected.
- Note the scan numbers needed.
- Run the program
GARED.
This will need bit parameters to steer the program, and when you finish
this section the program will interactively ask for
the first scan number, the number of scans and the record number
(=scan number now). Give a negative scan number to go back to parameter
settings, or zero to exit.
Bit parameters in use at present are listed in
Reduction of galactic observations on the HP computer.
- On the terminal next to the one where the observation is running type:
BR,OBSRV
This will take a few seconds for the telescope to finish the current pointing.
If you must urgently interrupt the current scan use:
RU,REGIS
15,1
-1/
At this point you can use BR,OBSRV as above.
- Make sure that the lineprinter is online.
- When the system prompts with
NEXT SOURCE?
Type in N (for 'no') and RET. The program will then stop
observing , give the message
OBSERV STOPPED
and make a listing of observations done on the lineprinter.
Note at the appropriate places in the logbook and on the
printout of the observing schedule that you stopped the observation,
and give date and time.
- Stop any schedule running (see above).
- Remove the telescope from computer control, and
set the position to Azimuth 134.541 and elevation to 0
using the `sweep' on the manual telescope control unit.
(See below `Pointing the telescope by hand').
Check that the correct values are given on the displays of azimuth and
elevation.
- Check that the lamp `Hefplateau' is on for azimuth 134.541
and that the elevation is in its end-switch.
- At this point the telescope will be in the correct position for
technicians to work on the frontend.
The procedure to take the telescope back is as follows
- Check that the frontend is connected properly, and that the
`Hefplateau' is taken down.
- Increase the elevation (manually) to above 10 degrees.
- If this is a different frontend, check and if
necessary change the default frequency parameters in the file
`INFOFL' using the program
INFFL.
- You may now check the frontend and restart the schedule.
A version of this procedure by Moorrees is available in Dutch,
See section Handleiding bij Storm.
- You notice that a storm is raging outside.
The 'storm' refers to a wind force greater than Beaufort 7,
and the current wind can be checked in the telescope on the Weather Station
(unit
W103-Z) and the Wind Meter (unit W103).
- A weather forecast predicts wind force greater than Beaufort 7.
- The head of the telescope group or operator decides that this
procedure is needed.
- Check whether an observation is running (see procedure
on `Checking current observing status').
- Stop the observation and note the date and time in the log book
(on the console table) at the appropriate place.
- The telescope's own storm protection system should point the telescope
to the zenith.
- If the storm is of force greater than Beaufort 8,
put the clamps on the wheels, and note the date and time in the log book
(on the console table) at the appropriate place.
- Place the clamps so that the clamps are in opposite directions
on opposite wheels; i.e. before one wheel and behind the opposite wheel.
- Set each clamp so that they attach from under the rail track and from
above onto the wheel.
- If this procedure has been done by someone other than the telescope
operator, then put a note into the the telescope operator's mail box.
If this procedure has been done by someone other than the head of the
reduction group then put a note into the head of the reduction group's
mail box.
- If the wheel clamps are on, remove them.
- Set the elevation of the telescope to below 85degrees. This is
needed because the schedule cannot (by default) point the telescope
above this elevation.
Note that you have reset the elevation in the logbook.
- Edit the schedule to remove all observations already done, and those
missed so that only the section remaining to be done is left. Give the
new version of the schedule a new file name, and note this in the logbook.
- Print the new schedule out, and keep the listing by the logbook.
- Start the new version of the schedule, and note the date and time in
the log book.
- Check that the new version of the schedule starts observing the
correct source, and that the telescope is behaving normally.
The buttons to choose between telescope control by hand and by computer
are on leftmost rack at about chest height (unit 90-79-3),
with a black line above marked:
Computer Azimuth RT bedrijf Elevatie
----------------- ----------------------- ------ ------------
[El] [Az] [El/Az]| | | | [In] | | |
| [ ] |
Leave the RT bedrijf button in at all times.
- Stop any schedule running (see section `Stopping an observation')
- Remove the telescope from computer control (yellow
El and
Az switches to 'out' position ).
- Use the elevation dial to set the azimuth and elevation
The current azimuth and elevation (in degrees) can be seen on the display,
units
90-57.
- When you are finished, return the telescope to computer
control (yellow
El and Az switches to 'in' position ).
- Extract the text file (
filename).
Normally the schedules arrive as e-mails or files on a workstation,
so that the first part (extracting the schedule text file)
depends on the details of the arrival and the workstation.
For mime files attached to mail:
Choose a convenient filename so that it is possible to see
which period it corresponds to.
- Print out the schedule listing to check that it is correct,
and for use in the telescope.
- Find a tape unit and set it to 1600bpi using the front switches.
- Mount a new tape with a write ring.
- Write the file to a 1600bpi tape.
This makes the (variable length)
input records into (fixed-length) 80byte records on the tape on the SUN
tape unit:
awk '{printf("%-80s",$0)} filename | dd of=/dev/rst12 bs=80 conv=block
- Bring the tape and schedule listing
to the telescope and dump the tape to file
filenm
with the command:
ST,8,filenm
Note that the HP-1000 system does not support filename
extensions.
- Check the schedule with the program CHKINP. Error
messages can be checked against the schedule listing.
- If the file is correct, start the schedule with OBSRV
When a schedule finishes, the scans observed will automatically
be listed to the line printer.
Use the program GCOPY to write the scans to tape in the
Dwingeloo format.
- Check which scans (=records) are needed, and the name of
the data file used (GAFIL1, GAFIL2 or GAFIL3).
- Make sure that there is a new tape on the HP tape unit
(
ZWO 999)
with a write ring.
- Check that the tape is loaded and the unit online.
- Start the tape dump.
This is done by:
RU,GCOPY,,,-1,,MT
The program will request the following items:
- The data Filename
- The First scan number to write
- The number of scans to write
- The subscans ignore this item
- Whether to change scan numbers do not do this
- The First record number (identical to scan number).
End all entries with the '/' character.
- Wait until the program ends before removing the tape or
stopping the printer.
If the terminal has been out it will need to be reset, so
use the following sequence (from Galactic Observations with the
Dwingeloo Telescope).
- Start the configuration with the keys CTLF1
- Choose the language option with F1
- Press RET
- At this point the display should show the following:
Baud rate Parity Duplex Straps Handshake Hz Start Col Return
9600 None(0) FULL abcgHxz Etx 50 1 (Cr)
If any of these items are incorrect, use the TAB key to move
to that item and the NEXT or PREVIOUS key to get the correct
setting.
- When all items are correct, press the yellow key at the bottom
of the keyboard.
Astronomers wanting observing time on the Dwingeloo Radio telescope
should follow these steps:
- Write a proposal with a list of technical requirements
(observing mode, frequency, bandwidth, amount of observing time) and
up to pages of scientific justification and figures.
This proposal should outline how the scheduling, and data reduction
will be done, and the format needed by the astronomer.
- Send the proposal to the Head of the Reduction group in Dwingeloo,
for a technical evaluation, and the Chairman of the ASTRON
Program committee (currently Thijs van der Hulst in Groningen) for
a scientific justification.
- If the program is accepted the Head of the Reduction group
will contact the astronomer about scheduling details.
@c________________________________________________________________
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