Here are minutes of our meeting on Thursday -- please just reply with, or let me know, any corrections -- thanks!:
Phoning in: Yorke Brown (Dartmouth), Arnold Gaertner (NRC), and Karun Thanjavur (UVic) (regrets from Cordell Grant (UTIAS-SFL))
At 5 am this past Saturday morning (June 28), we launched ALTAIR-13 from the grounds of Thetford Academy in Vermont and, within a few seconds of launch, lost telemetry contact with the vehicle at the Thetford launch site. The recovery/science site at Robert Frost Lane in Etna NH 15 km downrange received a single burst of telemetry a few seconds after launch before they too lost all radio contact. As we were unable to contact the gondola, there was no way to cut the gondola loose from the balloon, so it floated up to its burst altitude (likely around 25 km) rather than the 7 km altitude we had intended to reach on this flight, then burst. Paul, who together with Yorke and Victor was at the recovery/science site, was able to visually (and additionally with a good pair of binoculars) find the balloon high in the sky approximately 40 minutes before we observed it "wink out" as it burst. After the burst it is quite likely that the parafoil was shaken loose from its clip, but as the parafoil was in a straight rather than a turn position (having the parafoil in a turn position, and the gondola thus fall in a helix, ends up with a landing site far more akin to the fall of a regular parachute than having the parafoil in a straight position, in which the parafoil sails along for a long way in a single direction, most likely with the wind), it is likely that ALTAIR 13 drifted along for a very long way south (possibly to somewhere near the NH - MA border) and is probably somewhere at the top of a tree in the few thousand sq. miles of mostly forested possible landing area in that region.
The best hypothesis so far, from Yorke, on why we lost telemetry, is that the centre pin of the SMA connector between the dipole antenna and the ALTAIR gondola was loose, and there was just a single burst of intermittent electrical contact before the connection was lost entirely. Clearly visually inspecting that contact will be a necessary addition to the preflight checklist. A necessary addition, but not a fully sufficient addition, as this is just a good hypothesis, and there are a number of other reasonable possibilities (e.g. that the gold coating of the contact was stripped rather than the centre pin being loose, or that the RFM DNT-900 RF receiver chip that we use had simply gotten worn out, perhaps due to the effects of reflected power from being turned on without an antenna attached), so both Yorke and I are of the opinion that having some form of backup telemetry will be necessary as well. For backup telemetry, two possibilities that Yorke is presently thinking of are 1) having a second DNT-900 (with second dipole antenna) onboard, which (to avoid interfering with the primary link) would have to only be switched on if we lost the primary radio link, or 2) something in the 433/434 MHz ISM band (which, unlike the 910 MHz primary telemetry band, is not license-free in North and South America, so if we added this, in a somewhat similar way to having a second DNT-900, it would also have to normally be off, and we [specifically a licensed amateur radio operator on the team] would only use it for very brief tests or if we lost the primary telemetry).
Fortunately we were not flying the O($15k) laser-diode-module-and-integrating-sphere-based science light source, and instead were just flying the simple (and very low-cost, O($30)) LED board-based engineering light source, so nothing extremely expensive was on board.
Anyway, Yorke and Cynthia are making excellent progress in building a new gondola, which will have many improvements that Yorke has been planning for awhile (and not just backup telemetry), and we should be flying again before long (and very likely before the end of the summer).
Regarding laboratory and computational modelling of the light source(s), Karun is making progress on Zemax-based computational modelling, and Divya, Ryan, and Victor are making progress on Angora (FDTD open source) based computational modelling. Karun also just had the UVic machine shop finish making a useful part for laboratory source measurements. I'm working on some analytical modelling of diffuser-based light sources. For integrating sphere-based light sources, Karun et al's computational modelling with and without different baffles in place will study whether a baffle and/or a diffuser in our next set of integrating spheres will be useful for us. As soon as we have a design for a baffle or diffuser, we'll hand that to Allied Scientific Pro and World Star Tech respectively.
On computing/website, things generally appear stable -- please just either post a note or let me know if any fixes or changes are needed.
Regarding grant applications, I've contacted Dale George regarding ordering a (single) superpressure balloon, which will be useful for determining (following the future point at which we attempt to fly it) whether we want to add additional balloons of that type to upcoming grant requests, and Dale has now asked me to send him a set of detailed specifications. There also is, of course, much recent interest in U.S. grant applications, which could of course focus on nanosat, balloon flights, or both. The best focus there would likely depend on the requested budget, which in turn depends on granting program. Susana and Nathan will perhaps be visiting Hanover NH sometime this or next month in order to take a closer look at the current ALTAIR gondola and payload design and flight procedures, for grant request purposes and to better develop shopping lists for JHU students.
That's all I remember, please send things that I forgot. Next telecon as usual in two weeks, on Thursday, July 17, at 2:30 pm Eastern time.
cheers, thanks all! justin
On Thu, 03 Jul 2014 04:24:58 GMT, Justin Albert wrote:
> Hi, > > Telecon tomorrow (July 3) at our regular time of 2:30 pm Eastern time > (11:30 am Pacific, 20.30 European). Discussion items include: the > fateful ALTAIR 13 this past Saturday, construction of a new payload, > toward "bulletproof telemetry", status of light source studies and > modelling, goniometric and pre- and post-flight calibration, nanosat and > new laser module design, computing/website, grant applications, and > planning for the rest of the summer. A reminder of the CSA project > timeline is attached. > > Here's the dial-in info: If you are calling in from Canada or U.S.: > 1. Dial Toll-Free Number: 866-740-1260 (U.S. & Canada) > 2. Enter 7-digit access code: 5082741 followed by the # > > If you are calling in from elsewhere: > 1. To locate International Toll-Free Numbers go to > http://www.readytalk.com/intl (enter 7-digit access code 5082741) > 2. Dial toll free number from web link > 3. Enter Passcode: Enter 7-digit ACCESS CODE: 5082741 followed by the # > > Here's the tentative agenda: > I) ALTAIR 13 > II) Construction of a new gondola and payload, and robustness improvements > III) Light source studies and modelling, pre- and post-flight calibration, and goniometric calibrations > IV) Nanosat, new integrating spheres, and multicolour laser module designs > V) Computing/website > VI) Grant applications > VII) AOB > > Talk to you all tomorrow, > justin > > Attachments: > http://projectaltair.org/HyperNews/get/AUX/2012/11/12/18.02-43361-Schedule-20120702_hqp.pdf >