SUG 30 July 2013 (Andy, Chuck, Dave, Dick, Francisco, Jim B, Tom, Wes)
July 30 comments in bold
System Diagrams
System diagrams and other info is at the new Jove web site. http://www.radiojove.org/SUG/ . Please make sure your diagrams are correct and current.
Storage – archival and workspace
(No discussion during 30 July meeting.)
Spectrograph data storage rate is approximately 165 MB per 12 hours per instrument (14 MB/hr). Dave is operating the UFRO machine and a dual spectrograph for RCP and LCP – for this count lets call that 3 instruments. Other stations are Wes 1, Jim B 1, Andy 1, Tom A 1). This yields a current total of 7 instruments producing data at a rate of 14MB per hour each, for a total of 98 (call it 100) MB per hour. The total predicted duration of Io-related storms for the 2013-2014 season is 118 hours which results in11.5 (call it 12) GB of data. This of course only accounts for Io related Jupiter activity and neglects non-Io activity and solar. Just a WAG, but lets add in another 100 hours per year for solar and non-Io events so the annual total is (7 spectrographs x 218 hours x 14 MB/hr) = 21 GB. By comparison, each instrument recording and saving 24/7 is 123 GB saved annually on each local station hard drive. All 7 instruments together, running continuously, are generating 858 GB (almost a terabyte per year). Given the above estimates, we are planning on storing in shared workspace/archival space less than 2.5% of the total data collected. Where, and for how long data will be stored has yet to be decided (short term workspace vs long term archival). Suggestions welcome from all re short term vs long term.
Reports
Dave has posted a report template on the web site. It was decided to use this report template only for Jupiter storms and that we would try to use the Observer Log feature of SkyPipe for the observer to enter comments during storms. The report template was modified slightly and it was decided that the TEC and Lightning maps do not need to be included in each individual station report but that these maps will be posted to the SUG webpage for eventual use in the final storm reports. Andy suggested the SUG Web page be expanded to include links to papers of interest (for example galactic background info). Also the SUG meeting minutes will be archived there.
Science
Chuck previously sent around 5 questions may be addressed by spectrograph observations. – These are listed below.
- Modulation lane characteristics – drift rates for source types, beaming models
- Arc structure for sources --- could help with cone structure and beaming parameters
- Polarization Info – statistics for source information, switching modes or source hemisphere
- S-burst structure – drifting, splitting, quenching, models, etc.
- N-burst structure – source?
Discussions of N-bursts and S-bursts continued. Chuck has sent the GAGE 1220 high speed digitizer to Dave. It will be used in conjunction with Wes’s tuneable wideband receiver to capture S-bursts in high resolution. Dave and Wes have made preliminary measurements of the receiver performance. Wes and Dick are implementing some upgrades to the receiver including a crystal controlled first LO, and an anti-aliasing filter. Francisco is assembling historical data showing Io/CML when N bursts are most likely. Wes, Dave, and Dick are going thru old spectrograms to compile information on N-events.
If N-burst activity is observed this upcoming season an attempt will be made to observe it in higher resolution by narrowing the sweep range of one or more of the spectrographs. Also the high speed digitizer may be used. The spectrographs will be a valuable aid in tuning the wideband receiver to the frequency where activity is occurring.
Chuck sent out a paper related to GB temp and there was discussion about measured temperature of the GB temp and if it was dependent on polarization of the receiving antenna. This paper (or a link to it) will be placed on the SUG site in the new library section.
Overlay and Common Settings
The ability to overlay spectra from different stations is an important first step. Problem is that different stations may be operating over different frequency ranges, using different color and offset settings and even different color pallets. The original idea was to decide on common settings to be used by all stations. Dave offered an alternate idea that appears to have a lot of merit. He feels that it will be possible (within limits) to normalize data from different stations and perform the overlay operation in software. In other words we can use whatever color gain/offset/color pallet we like at each station for the data that is streamed over the internet. Later, the raw data can be normalized (in frequency, time and amplitude) in software to allow valid data overlays and comparisons. In order to perform the normalization of spectrograph data an amplitude calibration is necessary. Dave will generate an array of numbers representing the spectrograph ADC input voltage for each channel the spectrograph vs a range of input temperatures.
Dave raised the important issue of how many spectrograph channels to run at different stations. This is a critical issue related to overlay and comparison of spectrograms. We are trying hard not to constrain any observer to a particular streaming data format (gain, offset). However, some observers favor collecting raw data at 400 channels and others 200 channels. Dave is currently constrained to 200 channels on the old UFRO machine (connected to the 4 element SuperJove array) and the Dual Polarization Spectrograph (connected to the TFD array).
The spectrograph sweep speed is constant meaning it dwells on each channel for a fixed time interval. For 200 channels this means about 10 sweeps per second. For 400 channels one gets 5 sweeps per second. You cant increase frequency resolution without paying a penalty in time resolution. This is an important problem for future discussion. It may be that there is a software or firmware solution that Jim Sky can provide; but, even in that event, we need to discuss the merits of the different resolutions.
Calibration
Dave and Wes resurrected a 5722 standard noise source. This was used to calibrate an HP461A which will be sent to SUG stations to calibrate their spectrographs. Dave has generated procedures for use in the calibration procedure (with editorial nit-picking by Flagg). This is the first step in stations being able to generate comparable data and work toward characterizing received signals in terms of Janskies. Jim Brown has purchased an HP461A (e-bay) and will use that along with a step attenuator from Wes. The 461 has been calibrated in Florida. The loaner noise source has been sent to Andy who has used it to calibrate his system. Next it will go to Jim B and then to Tom A. Dave will analyze Andy’s data before the unit is shipped to Jim.
Lightning Protection
Brief discussion of driving ground rods into rock.
RSS Upgrades
No new discussion
Homework
Francisco will develop more info on N-events and (IO/CML)
Wes will send out info on a stereo digital recorder for high quality audio recording.
Wes and Dick will continue their efforts to find N-events in old UFRO spectrograms.
Misc.
Tom attended his first SUG meeting – welcome Tom!
Tom has purchased a Jove dual dipole for use with his spectrograph. Andy will obtain a new Jove receiver. Jim Brown is hard at work on his antenna upgrades for the new season. Happy trenching Jim!! Dave is experimenting with inexpensive 16:1 transformers from Mini Circuits to reduce the cost of the Terminated Folded Dipole (TFD) antenna.
NEXT MEETING 13 Aug 5 PM EDT 888-558-3493 113500#
rf 30 July 2013