Review at Software Group Workshop (LPL, 29th April 2009)

Present : B.Burleson (chair), M.Ford (minutes), P.Conway (guest delegate) :-

• requirements for SEMS :-

• environmental asset protection
• essential environmental observing measurements

• current system has two decision levels :-

• asset protection (critical measurements)

• if critical sensor is not reading or has failed, assumed it is 'Bad'

• suitability to observe

• if non-critical sensor is not reading or has failed, assumed it is 'Good'

• two-level system has been unpopular :-

• not always easy to tell at-a-glance why the telescope is closed
• are the two levels the problem, or the lack of RCS telemetry
• suggest the lack of RCS telemetry is actually the problem (e.g. no countdown for 30 minutes)

• proposed states in SEMS/jTCS ICD :-

• Good
• Bad
• Failed
• what if asset protected but non-critical sensors out of range (e.g. cloud) ?

• proposed reporting of weather/environmental states :-

• SEMS reports state with respect to asset protection

• Sequencer reports state with respect to suitability to observe

• proposed that SEMS has non-critical sensors :-

• wind direction

• solar power

• barometric pressure

• sky brightness

• also proposed that SEMS has additional critical sensors :-

• particulate monitoring

• electric field detection

• with respect to proposed new critical sensors :-

• if mandate is "bias to observe", why new sensors to determine reasons not to ?

• if these sensors are so critical, why are they not being fast-tracked to the 2.0m FT sites ?

• scope :-

• site-wide :-

• SEMS is a site-wide facility, measurements are site-wide
• what if, for example, 0.4m wants to observe in higher humidity than the 2.0m ?
• does critical sensor thresholding need to be done on per-observatory basis within a site ?

• observatory-specific :-

• SEMS state is observatory specific, worst of multiple telescopes

• telescope-specific :-

• Sequencer is telescope-specific, makes request to open and observe

• Data Logger has hardwired normally-on Close signal to enclosure(s)

• existing SEMS proposal :-

• hardwired signal is 0th level of weather state (most extreme)
• software thresholding process perform 1st level of weather state thresholding
• hardwired signal inhibited by software heartbeat from thresholding process

• issues with existing SEMS proposal :-

• introduces an additional level of weather state (from 2 -> 3)
• software heartbeat inhibiting hardware signal is implicitly unsafe

• e.g. thresholding process fails but software heartbeat thread remains running

• how is this hardwired state reported to PubSub ?

• e.g. if thresholding/PubSub process failed, who reports the hardwired signal ?

• with digital sensors (e.g. wetness), software and hardwired close triggered at same time

• should the hardwired signal latch ?

• revised SEMS proposal :-

• critical (asset protection) thresholding not done by software process interfacing to PubSub
• critical thresholding done on Data Logger
• no software heartbeat to inhibit the hardwire signal
• hardwired signal is the normal close mechanism for asset protection
• hardwired signal does not latch, i.e. clears when weather clears
• hardwared signal is (also) reported by each enclosure/dome as an input
• for sites with multiple observatories, Data Logger has for each observatory :-

• a hardwired output for each observatory's enclosure
• an optional set of different thresholds for each observatory

• Data Logger configuration will depend on the observatories present at a site

• optional sensors :-

• become part of site-specific instances of SEMS

• external weather feeds :-

• not to be read by Data Logger, even if it has the capability to do so
• external feed cannot be a critical measurement

• Boltwood :-

• is sacrificial computer a better implementation that the virtual serial port ?
• Data Logger could read from Boltwood sacrificial computer via HTTP - NO
• is Boltwood part of SEMS ?

• yes, it's under full LCO control

• can any Boltwood measurements be critical ?

• no, concern about reliability and accuracy

• summary :-

• SEMS contains sensors under full LCO control, read by Data Logger

• Core sensors
• Optional sensors for site-specific instances - these can be critical

• LCO-controlled network feeds (e.g. Boltwood)

• no examples in existence to be part of Core sensors
• may be Optional measurements
• cannot be critical (can be used in suitability to observe at higher level)

• external weather feeds

• no examples in existence to be part of Core sensors
• may be Optional measurements
• cannot be critical (can be used in suitability to observe at higher level)