Note the comment made towards the end of this letter: ---- From cwalker@aoc.nrao.eduMon Apr 19 14:49:20 2004 Date: Mon, 19 Apr 2004 11:50:04 -0600 To: Paul Kondratko Cc: 'Craig Walker' , vlbiobs@revere.aoc.nrao.edu Subject: Re: BK110 Schedule Paul Kondratko wrote: > Dear Craig and Lisa, > > I am submitting the SCHED file with this e-mail. The most significant > change to the schedule is that it is actually running now. ;) > > To ensure that I am using the most recent version of SCHED, I used the > version of SCHED on aspen. I am still concerned about the following three > things: > > 1) SCHED complained that it cannot recognize my VLA frequency setup. Craig, > I would greatly appreciate if you could check if I am configuring the VLA > properly. I want to cover a velocity range (Helio, Radio) of 3016-4365 > km/s, which corresponds to sky frequency of 21.9101 - 22.0101 GHz on DOY > 117/118. I have VLA IF A (RCP) configured to cover frequencies 21.9101 - > 21.9601 GHz and VLA IF D (LCP) to cover frequencies 21.9601 - 22.0101 GHz. The frequency setups do not include any with AC at different frequencies from BD (the list would get huge). Otherwise I have built a lot of checks into SCHED (more than I can remember) so if it is not complaining, you are most likely ok. I did look at the setups and don't see any problems. > > The target lines are at least 7 MHz away from the edges of the 50 MHz VLA > bands. A visual inspection of the "Bandpass Calibration" VLA web page > indicates that this offset should be sufficient. > I think you will be ok with this. As I think I mentioned earlier, the phase curvature won't show in VLA bandpasses because it is the same on all antennas, but is seen in VLBI to other antennas, and in the recent tests of the first EVLA antenna. > 2) the VLA overhead. I have DUR=40s scans and SCHED reports VLA slews of > ~-19s. Does this mean I will have roughly ~20s of data from the VLA per > scan? That is right. The 19s is 4 seconds of slew and 15 seconds of setup. And there is the 10s granularity problem that I mentioned earlier. That 15 seconds includes something like 5 seconds for that granularity but that is just an average. So the offset can be anywhere from 10 to 20 seconds. I did check since my last message and the on-line system stays in a scan to the requested end, then waits for the next 10s IAT boundary before starting to do anything like slew. > > 3) Following your suggestion, Craig, I mistuned the unused VLA bands. > However, I am seriously concerned about how the correlator and AIPS will > treat the unmatched channels. If there are problems, they can be fixed and we will do that. It might take some fiddling by Barry, but he said to go ahead. Craig By the way, have you looked at the bk110sch.ss files? They have some more detailed station specific information that you might find useful. > > I again apologize for my belatedness. > > Best Regards, > > Paul > > -------------------------------------------------------------------- > Paul T. Kondratko Harvard-Smithsonian Center for Astrophysics > 60 Garden Street, Mail Stop 10 Cambridge, MA 02138, USA > Telephone: (617) 496-3433 Fax: (617) 495-7345 -- --------------------------------------------------------------------- R. Craig Walker Array Operations Center cwalker@nrao.edu National Radio Astronomy Observatory Phone 505 835 7247 P. O. Box O Fax 505 835 7027 Socorro NM 87801 USA --------------------------------------------------------------------- From cwalker@aoc.nrao.eduMon Apr 19 14:52:56 2004 Date: Mon, 19 Apr 2004 11:59:46 -0600 From: Craig Walker To: "VLBI Observers (Aspen only)" Cc: Paul Kondratko Subject: Re: BK110 Schedule VLBI Observers (Aspen only) wrote: > Hi Paul and Craig, > > I've processed the most recent version of this file (April 18, > 23:25) and have some questions about it. > > The projected correlation rate is over the limit of 1000 kb/s. > Since the modes are switching we'll have to correlate those > chunks of time separately. Craig - do you think that will bring > the rate down? This is a 512 Mbps observation so it has to be processed in 2 passes, one for each tape. SCHED does not take that into consideration when calculating the bit rate so I think he is ok. > > Paul - you asked for a week's delay for 'improved EOP parameters'. > What parameters are you referring to? EOP are the UT1-UTC and pole positions that we get from the USNO. The USNO tables first have projected values, then are later updated to measured values. He wants the measured values. But there is also the issue of station locations. As far as I know, the set that is consistent with the source positions and EOP have not yet been installed. Also the ones we are old enough that the rates aren't too good and the extrapolated (for plate motion) positions we are using for today can be in error by up to about 10cm. I'll talk to John Benson and twist his arm to get on with installing new positions that we already have. Craig > > thanks, > > Lisa Foley > NRAO Data Analyst > -- --------------------------------------------------------------------- R. Craig Walker Array Operations Center cwalker@nrao.edu National Radio Astronomy Observatory Phone 505 835 7247 P. O. Box O Fax 505 835 7027 Socorro NM 87801 USA ---------------------------------------------------------------------