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Telecon tomorrow (Thursday) @ 5 pm Eastern time

Hi all,

Telecon tomorrow (Oct. 1 in North America, Oct. 2 in Australia) at the regular time: 5 pm Eastern (2 pm Pacific, 11 am Hawaii, 23.00 European, 7 am Eastern Australia). We have more updates on more testing of, and the necessary guard ring addition to, the present version of the new transimpedance amplifier boards for the photodiodes. We additionally have recent updates on AIFCOMSS, and on the 144 MHz transceivers (Raveon and Radiometrix). 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 a progress report 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@uvic.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!!!

-- jalbert - 2020-09-30

Hi all,

My apologies for the delay! -- here's an update on recent ALTAIR balloon work, minutes of the meeting two weeks ago (attendees Arnold Gaertner [NRC], Liviu Ivanescu [Sherbrooke], and me), and a reminder of the telecon in 15 minutes(!) from now:

While working on our transimpedance amplifier board update to include the guard ring, and to complete the lab testing all of the present board's properties in the hope that the next board update can be the final one, electrical engineering student Evan Moore found and -- just last night -- fixed a major source of noise in the present board. To quote his e-mail to me this morning:

On Thu, 1 Oct 2020, evanmoore wrote:
> Made a major breakthrough in testing the TIA last night. I was probing
> around the TIA module and I found that there was a very large ripple on
> the 2V5 rail that provides the voltage reference to the ADC. After some
> testing I found that this was because the 100nF of decoupling
> capacitance (C21) was causing the buffer op-amp providing that rail to
> oscillate (it was rippling at around 300KHz at 30mV pk-pk).
> Removing that capacitor (and thus stabilizing that rail) pushes the
> noise floor of the system *way* down (see attached, the "Cap ON" sheet
> is data typical of measurements taken before I removed C21, and Sheets
> 1-4 are all with C21 removed).
> Additionally, I tried attaching a photodiode cable (without the
> photodiode, shorting the ends together) and found that this actually
> improved the noise figure even more (sheets 3 and 4). Can't exactly
> explain why that might be the case but it is good to see nonetheless.
> So now, even without the Chop and SINC filters enabled on the ADC, our
> noise figure is approximately 100uV pk-pk. This is approximately 0.025%
> of our lowest expected signal of 0.4V (i.e. it meets the requirements as
> I understand them).
> When I enable both the Chop and SINC filters on the ADC, the noise
> figure drops by another order of magnitude down to 30uV pk-pk (at the
> expense of longer times to take each sample).
> So overall quite pleased with this result. Let me know your thoughts.

As a reminder, the schematic of the present board (note that the capacitor C21 is on the 4th/last page of this schematic) can be found at:

The noise that Evan originally saw can be found at:

and the new noise spreadsheet referred to in Evan's e-mail above can be found at:

With this fix, the board noise is definitely low enough for our purposes. So I've asked Evan to continue on with the layout of the board update, with the guard ring fix, no C21, etc -- and I am hoping that he will have that layout (+ renderings & schematic) in the next couple of days.

Radiometrix still has our four SHX1-144 transceiver modules (they arrived there on Apr. 6) and is doing their firmware update that solves the BUSY output issue. They'll then test them out and send them back to us. Due to the COVID-19 situation in the UK, they've been taking quite a while. Very fortunately, the COVID situation is slowly starting to improve in the UK (although everyone is of course very wary of a likely second wave). I asked Radiometrix about this yet again last week, and they replied that they are very busy, but will send a timeline and get to it as soon as possible... We've also been doing more connecting up and testing out of our two new 144 MHz Raveon M8S data modem transceivers here in Victoria:

After checking them out with Raveon's Windows-based Radio Manager software, I've started to connect the radios up to Arduino Megas -- in the next few weeks I'm planning to get them talking to one another, and then I'll check out their effective ranges.

Once we get those 144 MHz transceivers settled and back into the ALTAIR gondola, we'll do some outdoor drop testing of the actual gondola. (We've done all the outdoor drop tests I can think of doing with our dummy gondola.)

And 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 is in 15 minutes (!!!) from now -- see below for Skype instructions.

Cheers, talk in 15 mins (!) from now -- thanks all!


-- jalbert - 2020-10-01

Title Telecon tomorrow (Thursday) @ 5 pm Eastern time
Forum ForumGeneral
Topic attachments
I Attachment History Action Size Date Who Comment
PNGPNG EvanMooreNoise_problem.PNG r1 manage 55.8 K 2020-09-30 - 22:42 UnknownUser Measured noise in the present (no guard ring) TIA board
Microsoft Excel Spreadsheetxlsx TIA_rev1_low_noise_measurements.xlsx r1 manage 698.4 K 2020-10-01 - 20:35 UnknownUser Evan Moore's new TIA noise spreadsheet
Edit | Attach | Watch | Print version | History: r2 < r1 | Backlinks | Raw View | More topic actions
Topic revision: r2 - 2020-10-01 - jalbert
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