Telecon tomorrow (Thursday) @ 5 pm Eastern time

Hi all,

Telecon tomorrow (Mar. 11 in North America, Mar. 12 in Australia) at the regular time: 5 pm Eastern (2 pm Pacific, noon Hawaii, 23.00 European, 9 am Eastern Australia). Evan fortunately found after testing that switching to an AD8638 op amp (from the previous ADA4522-1 op amp) successfully resolved all known issues with the transimpedance amp board -- and we have now handed the design over to Andrew to make an ALTAIR form-factor version of the board. We have also now ordered the Guildline 1Mohm metrological calibration resistor (as well as a calibrated voltage source from Scotland), which will arrive next month. Also more news on other electronics work done by students Mike Huynh (on an electronics and optics vacuum testing rig) and Josh Gage (on the fabrication of laser diode heat sink assemblies), and a little bit more work on optical simulation from me. 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

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
VII) AOB

Talk to you all tomorrow, thanks!!!
justin

-- jalbert - 2021-03-11

Hi all,

My apologies for the delay! -- here's an update on recent ALTAIR balloon work, minutes of the last meeting on Feb. 25 (attendees Arnold Gaertner [NRC], Liviu Ivanescu [Sherbrooke], and me), and a reminder of the telecon in 15 minutes(!) from now:

After a lot of hard work, our electrical engineer Evan Moore very fortunately found that switching to an AD8638 op amp (from the previous ADA4522-1 op amp) on the transimpedance amp board successfully resolved all known issues (with a reminder that the most recent having been some excessive input bias current in the ADA4522-1) with the board. In order to do those tests, Evan needed to get rid of all ambient RF noise in the lab by putting the board in an improved Faraday cage -- here are photos of his setup:

and here is the Excel spreadsheet and plot of his Keithley 2450 current injection results, with all 3 curves being when using the AD8638:

Regarding the above plot (in Evan's words): "Series 1 is the first batch of data I collected from the ADC, when taken about 5 min after I powered up the TIA (I haven't turned the Keithley off for several days, so it is sufficiently stable now). Series 2 was the second batch of data, collected in reverse order (starting at 400nA down to -0.02nA which is what the Keithley reads at zero on this range)."

Here is Evan's comparison plot between the AD8638 and the ADA4522-1 (as well as also an AD4530, when deadbugged in order to deal with the different pin-out on that chip):

AD8638 looks the best. Evan has packaged all his board design files into a .zip file, and sent it to Andrew Macdonald, so that Andrew can work on the new ALTAIR version of the board. The differences between the ALTAIR version and the ORCASat version will be:

1) It will have the same ALTAIR board form factor as the previous ALTAIR TIA board, rather than having the ORCASat board form factor.

2) It will have 1 channel per board (as in the previous ALTAIR TIA board), rather han 2 channels per board (as in the ORCASat board).

3) It will have TIA gain ranges: 1k, 10k, 1M, 1G (as in the previous ALTAIR TIA board), rather than TIA gain ranges: 1k, 1M (as in the ORCASat board).

4) The boards should fit together as in the previous ALTAIR TIA board, rather than having 5 pos J1 and 12pos J2 connectors of the same sort as on the second page of the ORCASat board schematic.

5) In addition to a USB-miniB connector i/o to the PD (as in the ORCASat board), I would like to also have an SMA female alternative i/o to the PD (with the PD anode as the SMA/coax shield and PD cathode as central conductor -- and with just connections to PD anode and PD cathode -- nothing else on that connection as there are only 2 contacts in an SMA). (If there's room, Andrew will also put a triax as a third alternative i/o to PD on the board, but only if there's room.)

Otherwise, the circuit on the new ALTAIR TIA board will be exactly the same as on the ORCASat board.

I've begun to look some more at MEEP (https://meep.readthedocs.io/en/latest/) for finite-difference time domain (FDTD) simulation of integrating sphere output, but I haven't yet had time to make any significant progress there -- I'm hoping to do that in the next couple of weeks. It will be interesting to compare that with ray tracing simulations, when I can get a chance to do that!

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 a very long time; the UK is enduring its second wave of COVID, and with even-more-highly-transmissible COVID variants, and the country is still under a lot of restrictions as a result. Our department electrical engineer Nick Braam sent them an e-mail back on Monday, Dec. 14 to check up on when they will (finally) be sending the firmware-updated SHX1 modules back to us, to which they still haven't replied. (We'll be sending another check-up message this coming week.) In the meantime, 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!

justin

-- jalbert - 2021-03-11