Re: GAS team balloon stuff

Kevin Reeve
 

The GPS sits vertical thin side up/down so the GPS antenna is point towards the horizon and not up.  There could be some reflection causing the issue.

However in my years of using GPS since the 1990’s altitude has always been a weird one. In the early days the military injected errors into the altitude stream to prevent it from being 100% accurate.

Not sure if they do it anymore.

Kevin



From: <BARC-HAB@groups.io> on behalf of Jared Smith <jared@...>
Reply-To: "BARC-HAB@groups.io" <BARC-HAB@groups.io>
Date: Saturday, June 17, 2017 at 3:54 PM
To: "BARC-HAB@groups.io" <BARC-HAB@groups.io>
Subject: [BARC-HAB] GAS team balloon stuff

Congrats on another successful launch and recovery! Max recorded altitude was 113451'. Max speed was 102.5MPH. It landed on the far side of the only meadow in the area (photos attached, also the APRS data dump). There was a notable part of the balloon that remained intact on the tether. This likely increased the descent rate a bit.

I'd suggest that the GAS team send Jake Peterson a thank you or gift card or something for taking much of his day to give us access and drive us in on his Polaris Ranger. He got us within .25 miles of it. Recovery would have been very difficult or impossible without his assistance.

As a cool bonus, I found a National Weather Service balloon payload (the model was LMS6 Radiosonde) within a few hundred yards of our payload (photo attached). It was launched last June. It's pretty wild to find two balloon payloads so close to each other! It came with a mailer and I've mailed it back for re-use.

The ascent rate was rather low. When I saw it was around 4.5m/s, I ran another prediction. The balloon followed this pretty closely and landed within 2 miles of the predicted landing spot. With the exception of last launch, our predictions are generally close if we get ascent rate correct.

There were VERY anomalous altitude readings on late descent. Here are the last APRS readings:
10:03:38 - 13953' - 62MPH - Just North of Paradise
10:04:58 - 9097' - 50MPH
10:06:19 - 3418' - 47MPH - At foothills. This is 2000' under ground!
10:07:38 - 7513' - 55MPH - Just above ground.
??? - 5974' - I got this beacon direct. This is also under ground.
10:10:19 - 10541' - 54MPH - 3000' above ground
10:11:40 - 8786' - 17MPH - 1000' above ground
10:13:48 - 6672' - 0MPH - 1000' below ground
10:17:49 - 7590' - 0MPH - 60' below ground

We then started getting beacons at the landing location/altitude which is ~7650'.

I have no idea what to make of any of this. These are big altitude errors - many thousands of feet. I see no scenario where an updraft would lift the payload like that. And this wouldn't explain the under ground readings. Any ideas? Was there another GPS logging data onboard?

Jared


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