SES-14 owner @SES_Satellites: Off-target dropoff from @ArianeGroup @Arianespace Ariane 5 means all-electric propulsion to take 4 weeks longer than planned to get to GEO. Sat in good health, no other issues. Still awaiting word from @OrbitalATK & @yahsatofficial on Al Yah 3.
Thread: Attempt at some #Ariane5 #VA241 analysis:Events:AOS for Natal tracking station was planned for 06m41sec - Looked NominalESC-A ignition was planned for 09m01sec - Looked NominalNatal tracking of ESC-A continued until 09m28sec after which tracking/downlink seemed lost.
This apparent loss is during ESC-A Phase 3 after despin and when it's tilting
ESC-A tracking seemed lost 27 seconds after ESC-A ignition, which is around 21.5 seconds into the tilting phase, which lasts 130 secondsThis is around 18.5 seconds before LOX valves are opened
SES-14 owner @SES_Satellites: Off-target dropoff from @ArianeGroup @Arianespace Ariane 5 means all-electric propulsion to take 4 weeks longer than planned to get to GEO. Sat in good health, no other issues. Still awaiting word from @OrbitalATK & @yahsatofficial on Al Yah 3.https://twitter.com/pbdes/status/956810114207543296Sounds like the orbit is off target, although probably not by much if the extra time to GEO is "only" 4 weeks for an all ion thruster powered satellite.
Quote from: Galactic Penguin SST on 01/26/2018 07:50 amSES-14 owner @SES_Satellites: Off-target dropoff from @ArianeGroup @Arianespace Ariane 5 means all-electric propulsion to take 4 weeks longer than planned to get to GEO. Sat in good health, no other issues. Still awaiting word from @OrbitalATK & @yahsatofficial on Al Yah 3.https://twitter.com/pbdes/status/956810114207543296Sounds like the orbit is off target, although probably not by much if the extra time to GEO is "only" 4 weeks for an all ion thruster powered satellite.SES-14 uses PPS-5000 plasma thrusters, which are designed for 200 mN thrust / 3000 s Isp. How many PPS-5000 thrusters for orbit raising and maintenance are on SES-14? Then one could compute the delta v resulting from a 4 week "burn".
I am so laughing it this turns out to be faulty antenna.
...SES-14 uses PPS-5000 plasma thrusters, which are designed for 200 mN thrust / 3000 s Isp. How many PPS-5000 thrusters for orbit raising and maintenance are on SES-14? Then one could compute the delta v resulting from a 4 week "burn".
Peter B. de Selding @pbdesAl Yah 3 owner @yahsatofficial says satellite is making its way to GEO orbit, but co is silent on orbital position & fuel budget. @OrbitalATK sat uses chemical propellant to get to GEO, then electric prop for stationkeeping during 15-yr life.
Quote from: calapine on 01/26/2018 12:15 amI am so laughing it this turns out to be faulty antenna. That would have been a highly unlikely scenario. The last 30 minutes of the mission pass over no less than 4 ground tracking stations. All of those would have had to have an antenna malfunction to not receive telemetry.If the antenna failure was on the vehicle side it would have to a multiple failure given that the telemetry sub-system consists of:- 2 separate central processing units- 2 separate telemetry transmitters- 2 separate antennaeWhat bothers me is the strange nature of this failure: orbital targeting was off AND no telemetry YET successful deployment sequence of the payload.All three elements are controlled from the VEB. And all equipment in the VEB is redundant.So:For no telemetry both telemetry sub-systems would have to be off-line.For successful payload deployment at least one sequencer sub-system (and the associated electrical sub-system) would have to be on-line.For the incorrect target orbit both inertial unit sub-systems AND/OR both GNC sub-systems would have to off-line OR the propulsion system on the ESC-A upper stage had to have failed.I for one will be very interested in what explanation the investigation will eventually come up with.
Quote from: calapine on 01/26/2018 12:15 amI am so laughing it this turns out to be faulty antenna. That would have been a highly unlikely scenario. < SNIP >
Al Yah 3 owner @yahsatofficial says satellite is making its way to GEO orbit, but co is silent on orbital position & fuel budget. @OrbitalATK sat uses chemical propellant to get to GEO, then electric prop for stationkeeping during 15-yr life.
Quote from: hoku on 01/26/2018 08:35 am...SES-14 uses PPS-5000 plasma thrusters, which are designed for 200 mN thrust / 3000 s Isp. How many PPS-5000 thrusters for orbit raising and maintenance are on SES-14? Then one could compute the delta v resulting from a 4 week "burn".Hi,I found: SES 12, SES 14 and SES 17 uses SPT-140 thrusters.( Fakel Kaliningrad, Russia )http://epic-src.eu/wp-content/uploads/14_EPICWorkshop2017_SES_EPIC-Workshop-2017-SES-Presentation.pdf
NASA had a station in Ascension until 1999, at which point ESA took over.
I would argue the telemetry failure could be related. If the anomaly was the stage attitude was wrong, and the stage antenna was no longer oriented to be visible to the tracking station(s).