BIT 2015 Flight from Timmins

Hi all,

tldr: We flew BIT friday night. It mostly worked. CNES launches are cool. PILOT is pretty.

Last Friday (September 18-19, 2015), CNES launched BIT at around 9pm from Timmins, ON. The batteries ran out at around 6:10AM, just before sunrise.

Launch Video: https://youtu.be/Ld4rhbKmDRo (by Richard Massey)

Flight GoPro: https://youtu.be/UUfNdlQNkbM (by Javier Romualdez)

Campaign GoPro: https://youtu.be/V9xtkmlnSGw (by Javier Romualdez)

Launch at ~2:25. Dawn starts at 5:40. Ends with the arrival of the recovery crew. Javier is reportedly working on a more epic timed version.

BIT performance: This is just from in-flight kst, so there is a lot more to analyze. It is super-preliminary and subject to bla-bla-bla etc....

i) All systems (except the GPS) functioned throughout the flight (the GPS failed at 1.4km altitude, so Javier logged in to the flight computer and implemented a command so Steve could specify the payload location manually.) We landed in the morning around 11 (?). Javier's GoPro survived the whole flight.

ii) the inner frame pointing was controlled to between 0.5-1" rms. The longest chunk was over an hour (limited in the end by the earth's rotation and our gimble range). Target was 2", so we are pretty happy about that!

iii) the FGM pointed to ~0.2" (around 1 pixel in the focal plane camera).

iv) the PSF of the telescope was... rich and interesting. The central blob was ~1 pix by 5 pixels, with more structure outside of that. We clearly need much better optics.

CNES launch:

The CNES tow balloon launch is pretty cool:

-The payload sits on the ground until launch.

-A small tow balloon (with a small amount of positive lift) is attached to it.

-The flight train goes from the payload, through the tow balloon and attaches to the CNES instrument package (ballast, communications, etc) which lives at the bottom of the parachutes. This part of the flight train is slack until the main balloon grabs the payload during launch.

-another strap connects the CNES instrument package (orange and white box in the video) to a truck lined up with the balloon. The truck holds the tension from the balloon.

-the collars are removed during inflation.

-The payload is set up ~down wind from the balloon, but the balloon is not laid out exactly down wind.

-At Launch, the balloon is released; when the instrument package is well above the ground, it is released from the truck on the ground. Then the payload is released to be lifted by the tow balloon. The main balloon grabs the tow balloon and payload once it is high enough.

-The tow balloon is deflated after launch, but stays with the payload. It is smaller in angular extent than the balloon.

Pros and cons of the CNES approach:

-They can launch 2200 lbs (science) payloads on a 28 million cubic foot balloon (eg PILOT) but have never tried (as far as I know) anything bigger.

-The low level (30m - 300m) winds are much less important than for a truck launch - there was a lot of horizontal velocity at the PILOT launch, but the payload didn't care much since it was already 10m in the air when the big balloon grabbed it. The CNES mission manager said that they get more (5x?) launch opportunities at the same site as the crane launch does.

-the CNES communication package provides 1.4 MBps (down) internet that was really reliable throughout the flight. Could hardly tell we weren't still in the highbay.

-Integration was super easy: mount their little box and batteries, make sure the internet settings (IP, gateways, etc) are right, and have shackles above the pivot to attach to their flight train. No ballast hopper; no huge communications package; no strange communications protocol to interface with...

On the down side: the ballast is held in the instrument package, above, not under the payload, and so they rained 1mm diameter steel bee-bees on us when they dropped ballast at the end of the flight. Bare styrofoam surfaces are covered in embedded steel balls (but mylar easily stops them).

- Barth Netterfield