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Telecon tomorrow (Thursday) @ 5 pm Eastern time

Hi all!

Telecon tomorrow (May 19 in North America, May 20 in Australia) at the regular time: 5 pm Eastern (2 pm Pacific, 11 am Hawaii, 23.00 European, 7 am Eastern Australia). Although I of course want to, and always will!, keep these telecons focused on ALTAIR and not on ORCASat, there is some very ALTAIR-relevent news from our ORCASat pre-launch calibration at NRC in Ottawa this past week. Acoustic vibration testing (at another part of NRC, in another part of Ottawa, which I was not there for) had taken place the prior week (May 2 - 6); and during calibration this past week (May 9 - 13, which I was in Ottawa for), we found that one of the two photodiodes on the ORCASat integrating sphere is not reading out at all. This is the case for both the ORCASat flight spacecraft, and also the ORCASat functional prototype / witness spacecraft -- although it is the other photodiode on the prototype ( one of the two is the InGaAs photodiode, and on the other, the problem is with the Si photodiode). Alex Doknjas (ORCASat project manager) and I both tentatively suspect the custom cable assemblies that lead from the photodiode readout board (i.e., transimpedance amplifier and digitizer board) to the photodiode front-end modules themselves that are mounted directly onto the integrating sphere (each one containing only a single photodiode and a thermistor). The custom cable assemblies are USB-mini-B connector terminated with shielded 5 wire cable. We suspect it might possibly be cracking of some epoxy that was put on these cables during assembly in an attempt to ensure that everything held together during the vibration testing (and during launch). This is very important for ALTAIR because ALTAIR is intended to eventually share those same cable assemblies, photodiode modules, and photodiodes (although not the exact same photodiode readout boards) as ORCASat. It will be Friday this week (at the earliest), however, before Alex et al. get back to Victoria with both spacecraft and are able to open up the prototype in order to diagnose what is actually wrong, however, because Alex is flying back to Victoria tomorrow. More on this urgent issue in the progress report tomorrow.

Andrew Macdonald has made more progress testing his ALTAIR photodiode readout / transimpedance amplifier boards. I have some updates on (and some quite successful results with!) some new large lightweight flexible solar panels (for future balloon-top usage!) that have arrived here for testing, and also some more progress has been made with operation of the two Raveon M8S 144 MHz transceiver boards. More discussion items for tomorrow's telecon include: flight/telescope plans and tests; construction and lab tests of the new gondolas/payloads; light sources and light source modelling; goniometric and pre- and post-flight calibration; propulsion work; nanosat bus and payload solid models; computing / website / TWiki forums and e-mails; grant applications; and recap of schedules. I'll send the progress report and plots before the telecon tomorrow.

Here's how to connect:

1) Open Skype on your computer (note that of course, you should first install Skype, http://www.skype.com, on your machine if you haven't already).
2) In the "Contacts" menu, add me ( jalbertuvic ) as a contact, if you haven't already.
3) Just wait for me to Skype-call you at the usual time (5 pm Eastern, 2 pm Pacific, etc).
4) If there is any trouble, or if you don't get a Skype-call for some reason and would like to join, please just send me an e-mail (jalbert@uvicNOSPAMPLEASE.ca).

Here's the tentative agenda:

I) Flight & telescope plans, and upcoming tests
II) Construction, drop tests, and other tests of the new gondola and payload
III) Diffused light source and its modelling, pre- and post-flight calibration, and goniometric calibrations
IV) Solid modelling
V) Computing/website, including recent flight control and simulation progress
VI) Grant applications

Talk to you all tomorrow, thanks!!!

-- Justin Albert - 2022-05-18

Hi all,

My apologies for the long delay! -- here's the update on recent ALTAIR balloon work (and on closely related ORCASat issues), and the minutes of both the meeting 2 weeks ago on May 5 and the meeting yesterday, May 19 (both of those telecons had attendees Arnold Gaertner [NRC], Liviu Ivanescu [Sherbrooke], and me):

As mentioned in the meeting announcement on Wednesday: during ORCASat payload calibration at NRC this past week following acoustic vibration testing, one of the two photodiodes on ORCASat is not reading out at all. This is the case for both the ORCASat flight spacecraft, and also the ORCASat functional prototype / witness spacecraft -- although it is the other photodiode on the prototype (one of the two is the InGaAs photodiode, and on the other, the problem is with the Si photodiode). Alex Doknjas and I both tentatively suspect the custom cable assemblies that lead from the photodiode readout board to the photodiode front-end modules themselves that are mounted directly onto the integrating sphere. The relevant solid model renderings and drawings can be found here:

Here's a rendering of the whole ORCASat payload assembly:

The two cable assemblies in question (not drawn in the above, although their connectors are drawn) are the two short little cables that each make the 90 degree bend between each of the photodiode front-end modules:

and the photodiode readout board within the aluminum RF shield that is shown at the back of the rendering of the whole ORCASat payload assembly above (and is mostly behind the integrating sphere in that view). A drawing of the wiring of the cable assembly is:

and those cable assemblies were handmade by Evan around the beginning of 2021; and Alex, Tanner, and Ben added some epoxy to their connections during spacecraft assembly a few months ago in an attempt to make the connections between the connectors and cable more robust, but which might possibly have stiffened them to the point of cracking during vibration testing.

Alex will be opening the prototype payload on Tuesday, and he will thus be able to see what actually happened and why one photodiode is not reading out; we will see if the above suspicion is correct or not (I give it around 50% chance of being the cause -- there are a lot of other things that might instead be the cause).

Long ago (in early- to mid-2020) when those connectors and cable assemblies were chosen, instead of those, in my view, poorly chosen, USB-mini-B connectors and handmade shielded cable assemblies, I had wanted to use screw-in 4-position M5 connectors and (professionally-constructed and molded) shielded cable assemblies from NorComp:



but I was overruled by all the ORCASat students, who liked USB-mini-B connectors for some reason (they are more common commercially -- but that doesn't mean that they are better for technical usage in space or on a high-altitude balloon -- I think the screw-in M5 connectors are vastly better for such usage). Although I had been fairly insistent at the time, and I knew that handmade cable assemblies very likely would be a problem during vibration testing and at launch, I should have been even more insistent than I was back in 2020. We'll see after Alex opens up the prototype on Tuesday. Whatever fix we decide to make for ORCASat should almost certainly also be done for ALTAIR -- assuming of course that we aren't absolutely forced by time pressure to make a cursory fix for ORCASat, whereas we would certainly want to make a better and more solid fix for ALTAIR.

The ORCASat calibration work at NRC in Ottawa was, of course, absolutely critical in finding the photodiode problem! -- thank you very much especially to Arnold Gaertner, and definitely also to Eric Cote (NRC radiometry technologist) who did much of the very hard work, together with Alex Doknjas. A bunch of photos that I took during our calibration at NRC can be found in the directory:


We're all very greatly looking forward to going back to NRC to do calibration when we have both ORCASat photodiodes working (following new vibration tests) -- very hopefully in a couple of months.

Andrew Macdonald has also been doing a lot of hard work here in Victoria in testing the ALTAIR photodiode readout boards, and specifically in fixing a mysterious latch-up problem that appears to occur with them when turning on the reverse bias (but that doesn't occur with the ORCASat boards) -- but which hopefully can be avoided via good firmware procedures (specifically in only setting the reverse bias on or off before board power-up, and always maintaining that bias setting [either on or off] for as long as the board is powered up). More on that latch-up topic, etc, in a couple of weeks.

As mentioned in the progress report a couple weeks ago, we have three new Renogy 100 W flexible solar panels (and a controller which came with them, which we'll need to re-make for balloon use) -- with photos of the panels and controller at:


Summer student Adithi Balaji and I tested these solar panels successfully in sunlight 4 days ago on Monday, and we successfully charged a LiPoly battery from the three panels. Here you can see 2.7 amps coming from the panels and charging the battery:

Later this summer, we'll work on a new lightweight controller board for balloon usage.

The two 144 MHz Raveon M8S data modem transceivers are still here in my office (together with the LiPoly batteries that power them), and hopefully this weekend I will get a chance to test Colton Broughton's most recent code updates for them, which can be found in:


(as compared with his older code within https://particle.phys.uvic.ca/~jalbert/ALTAIR_M8S_Colton17nov21/ ).

Our new summer NSERC USRA student Adithi Balaji, Colton Broughton, Sarah Alshamaily, and Will Stokes have also completed installing AIFCOMSS ( https://github.com/ProjectALTAIR/AIFCOMSSwithCUPredictorTest ) on their laptops. I've updated AIFCOMSS to work with the recent Cesium v1.83, as well as the instructions, and they all report success with this update and those instructions. The next two things that we know most definitely will need updating (or, rather, creating) are the station-keeping software for AIFCOMSS, and the online command-handling within the onboard Arduino software -- and I'll also be working on those over the next 2 weeks.

Regarding the latest news on our four Radiometrix SHX1 144 MHz transceiver modules that were returned to us from Radiometrix (following their firmware update to fix the BUSY output):

and the problems that Colton found with them (i.e., that of the 12 radio TX to radio RX permutations between those 4 boards, only 3 of the 12 permutations work, 3 of the other permutations give spotty connections -- e.g. only around 1 out of every 5 characters gets successfully transmitted -- as if one is transmitting and the other is receiving on neighbouring channels, but not the same channel..., and the remaining 6 permutations do not successfully receive any transmitted characters) -- we sent an e-mail to Radiometrix to ask about this about 7 months ago. They then sent back an e-mail a week later asking for more information, and Colton replied to them the next day providing the info (just a query about what logic voltages we were using -- we've being using 5V TTL from our Arduino Megas). Radiometrix has not replied to us since that e-mail reply sent to them 30 weeks ago, and thus I pinged them 28 weeks ago to follow up, and again 19 weeks ago -- and Radiometrix hasn't replied to those yet either. I will be pinging Radiometrix on this yet again next week.

We also still need to test out our new DFRobot SEN0177 payload aerosol monitors that we have here:

Engineering students Josh Gage and Evan Moore found that the "wings" that Josh had found in the laser diode light output distributions:

were due to how the diode was mounted in the heat sink. When the diode is mounted properly and carefully, the wings go away.

We also have our 10 Hamamatsu S12698-01 photodiodes and 3 Thorlabs FDS100-NOCAN photodiodes (those Thorlabs ones have their windows removed) here in Victoria:

I've given them to Evan to try out -- he's taking a few weeks to ramp up, and will produce some linearity, etc., plots from them soon.

The survey-tripod-mounted device to cross-check yaw-pitch-roll information from the gondola (e.g., on days before/after flights) is also constructed now, thanks to Mark Lenckowski -- photo at:

and all that remains to be done is to finish the small fitting between the device and the bottom of the payload. The purchased hardware in it includes both the survey tripod (http://www.cpotools.com/cst-berger-60-alwi20-o-aluminum-tripod-with-quick-release--orange-/cstn60-alwi20-o,default,pd.html), two adjustable angle mounts (http://www.thorlabs.com/thorproduct.cfm?partnumber=AP180), and a rotation mount (https://www.thorlabs.com/thorproduct.cfm?partnumber=RP01). That last fitting to attach (temporarily, pre-or post-flight) the upper adjustable angle mount to the payload landing gear has been started and will be completed here in the next couple weeks.

We're currently revising the draft initial contractual agreement from our colleagues at Globalstar Canada regarding 2 initial SPOT Trace devices (and their service plans) for the educational side-project for the upcoming NATO SPS application, in which classrooms in elementary and high schools could launch company-donated SPOT Traces using party balloons (or a more environmentally-friendly version thereof), and track them to learn more about winds at different levels in Earth's atmosphere.

Houman will send Cordell and/or us updated sections of his master's thesis soon -- that information will be extremely useful to us going forward. Also, Susana and Nathan, it would be very helpful for us all to get the JHU students' final writeup when you have a chance.

Next grant application will be a NATO "Science for Peace and Security" application (together with Australian colleague partners).

Our next telecon will be in 2 weeks from now (on Thursday June 2, at the usual time).

Cheers, talk in 2 weeks from now -- thanks all!


-- Justin Albert - 2022-05-21

Title Telecon tomorrow (Thursday) @ 5 pm Eastern time
Forum ForumGeneral
Topic attachments
I Attachment History Action Size Date Who Comment
JPEGjpg ALTAIR_AndrewMacdonaldPhotodiodeReadoutBoardTIAFrontEndTestingRig_18may22.jpg r1 manage 4261.0 K 2022-05-19 - 22:21 JustinAlbert Photograph, taken 18 May 2022 by Andrew Macdonald, of Andrew's testing setup for the transimpedance amp front end of the ALTAIR photodiode readout board (purple)
JPEGjpg BatteryChargingFromRenogySolarPanels_16may22.jpg r1 manage 5786.7 K 2022-05-21 - 07:48 JustinAlbert Charging of a LiPoly battery from the 3 Renogy 100 W flexible solar panels on Monday, May 16, 2022
PNGpng EvanMoore29oct20cable.png r1 manage 18.4 K 2022-05-19 - 22:23 JustinAlbert Cable drawing from 29 Oct 2020 from Evan Moore
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