Topics

GAS team balloon stuff

Jared Smith
 

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


ag1t@...
 

I have only usually seen stuff like this when a GPS is used in the middle of town.  It is usually due to multi-path of the GPS signals which messes up the timing of the signal received by the GPS.  Then you get a bad reading from the GPS.
 
I have seen it on rare occasions in heavy green vegetation, but usually not above the tree line.  I wonder if the new green spring growth gave us a little multi-path?
 
Cool data Jared.  Glad to see Jake is still floating around.  Have not seen him in a while.  Just his wife Shelley.
 
Thanks for the pics.  Sorry I couldn't chase with you all today.  Getting a scout trailer ready for scout camp and a bad back make for a sore day.
 
  Gary

Tyler Griffiths
 

Great job guys!
Glad I could be of assistance even though I was not there.  

Tyler


On Sat, Jun 17, 2017 at 4:34 PM <ag1t@...> wrote:
I have only usually seen stuff like this when a GPS is used in the middle of town.  It is usually due to multi-path of the GPS signals which messes up the timing of the signal received by the GPS.  Then you get a bad reading from the GPS.
 
I have seen it on rare occasions in heavy green vegetation, but usually not above the tree line.  I wonder if the new green spring growth gave us a little multi-path?
 
Cool data Jared.  Glad to see Jake is still floating around.  Have not seen him in a while.  Just his wife Shelley.
 
Thanks for the pics.  Sorry I couldn't chase with you all today.  Getting a scout trailer ready for scout camp and a bad back make for a sore day.
 
  Gary

--
Tyler, Sent from Gmail Mobile

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


ag1t@...
 

Before 2000, the government degraded the signal (called Selective Availability).  Bill Clinton removed the limitation via Executive Order in 2000.

Most good GPS devices can be accurate within a meter now both vertically and horizontally.    

http://www.gps.gov/systems/gps/performance/accuracy/

Gary

Jared Smith
 

I thought that the uneven terrain and fast approach velocity (around 60 MPH) caused signal interference that caused the inaccuracies, but that doesn't align with the data.

Attached is a Google Earth view of the reported descent. You can see that it's rather linear from the near the top of the descent (by the way, it fell at 175 miles per hour after burst!) to where it should have hit the ground NE of Paradise. The problem is that the descent should have slowed as it got into thicker air and approached the ground.

Attached is a chart that compares altitude over time for the May 20 vs. June 17 flights. May 20 is normal, but today's flight increased its descent rate below around 15000 meters. Unless there's some other factor in play, this simply isn't possible. The red line indicates what I think was the actual altitude.

This suggests that the GPS was reporting inaccurate altitude for probably the last 15-20 minutes of flight - for every single position update until well after it was on the ground. I don't think that signal disruption could have caused that. I think this suggests a programming or internal issue, perhaps due to the cold temperatures.

I'd be happy to hear any other theories.

Jared
 

On Sat, Jun 17, 2017 at 8:38 PM, <ag1t@...> wrote:
Before 2000, the government degraded the signal (called Selective Availability).  Bill Clinton removed the limitation via Executive Order in 2000.

Most good GPS devices can be accurate within a meter now both vertically and horizontally.    

http://www.gps.gov/systems/gps/performance/accuracy/

Gary


Kevin Reeve
 

Good thoughts Jared.

We do know the GPS is the one that has flown as part of the Byonics MT1000 on all flights we have done.
We should check to see if it has come loose in the MT1000.

Another thought is the payload/tracking box is spinning rapidly and thus causing issues with receiving accurate GPS signals. The doppler effect per se.

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 10:30 PM
To: "BARC-HAB@groups.io" <BARC-HAB@groups.io>
Subject: Re: [BARC-HAB] GAS team balloon stuff

I thought that the uneven terrain and fast approach velocity (around 60 MPH) caused signal interference that caused the inaccuracies, but that doesn't align with the data.

Attached is a Google Earth view of the reported descent. You can see that it's rather linear from the near the top of the descent (by the way, it fell at 175 miles per hour after burst!) to where it should have hit the ground NE of Paradise. The problem is that the descent should have slowed as it got into thicker air and approached the ground.

Attached is a chart that compares altitude over time for the May 20 vs. June 17 flights. May 20 is normal, but today's flight increased its descent rate below around 15000 meters. Unless there's some other factor in play, this simply isn't possible. The red line indicates what I think was the actual altitude.

This suggests that the GPS was reporting inaccurate altitude for probably the last 15-20 minutes of flight - for every single position update until well after it was on the ground. I don't think that signal disruption could have caused that. I think this suggests a programming or internal issue, perhaps due to the cold temperatures.

I'd be happy to hear any other theories.

Jared
 

On Sat, Jun 17, 2017 at 8:38 PM, <ag1t@...> wrote:
Before 2000, the government degraded the signal (called Selective Availability).  Bill Clinton removed the limitation via Executive Order in 2000.

Most good GPS devices can be accurate within a meter now both vertically and horizontally.    

http://www.gps.gov/systems/gps/performance/accuracy/

Gary


Tyler Griffiths
 

That was my thought too. Spinning. 

Tyler 


On Sat, Jun 17, 2017 at 10:51 PM Kevin Reeve <kevin.reeve@...> wrote:
Good thoughts Jared.

We do know the GPS is the one that has flown as part of the Byonics MT1000 on all flights we have done.
We should check to see if it has come loose in the MT1000.

Another thought is the payload/tracking box is spinning rapidly and thus causing issues with receiving accurate GPS signals. The doppler effect per se.

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 10:30 PM
To: "BARC-HAB@groups.io" <BARC-HAB@groups.io>
Subject: Re: [BARC-HAB] GAS team balloon stuff

I thought that the uneven terrain and fast approach velocity (around 60 MPH) caused signal interference that caused the inaccuracies, but that doesn't align with the data.

Attached is a Google Earth view of the reported descent. You can see that it's rather linear from the near the top of the descent (by the way, it fell at 175 miles per hour after burst!) to where it should have hit the ground NE of Paradise. The problem is that the descent should have slowed as it got into thicker air and approached the ground.

Attached is a chart that compares altitude over time for the May 20 vs. June 17 flights. May 20 is normal, but today's flight increased its descent rate below around 15000 meters. Unless there's some other factor in play, this simply isn't possible. The red line indicates what I think was the actual altitude.

This suggests that the GPS was reporting inaccurate altitude for probably the last 15-20 minutes of flight - for every single position update until well after it was on the ground. I don't think that signal disruption could have caused that. I think this suggests a programming or internal issue, perhaps due to the cold temperatures.

I'd be happy to hear any other theories.

Jared
 

On Sat, Jun 17, 2017 at 8:38 PM, <ag1t@...> wrote:
Before 2000, the government degraded the signal (called Selective Availability).  Bill Clinton removed the limitation via Executive Order in 2000.

Most good GPS devices can be accurate within a meter now both vertically and horizontally.    

http://www.gps.gov/systems/gps/performance/accuracy/

Gary


--
Tyler, Sent from Gmail Mobile