How to protect bearings against cold (-60°C)

I am using a ball bearing mechanism to allow an horizontal rotation of the payload around the z axis, to compensate the rotation due to the wind.

To protect the bearings against the cold (-60° at target altitude), I found a grease made for that purpose, that is financially accessible.

It's made by the company "Univars" and is cold : Molykote 33 Medium Extreme Low Temperature Bearing Grease, and cost £11.

Here is the product :

How to increase the battery of a gopro

I ran into a new problem today. While working on the whole system, I forgot to ask myself how would the gopro be able to stand an 8 hours flight. This is way longer than most flights ! but some flights can long such a long period.

Two problems :

• size of the video : no problem, a simple 32Go will do for no. It's a 4 hours recording, but it will be fine to begin with..

• battery autonomy : That's the real problem. For a native gopro battery pack, it's a lipo 1100mAh, and you can last a little over 2 hours. So I told myself that it should be possible to plug a ubec into the gopro in order to use one of my lipos to increase the time. I finally found a solution on a post of someone using the USB connectivy to power the gopro via external power. He is using a 2650 mah lipo and managed to make a 6 hour timelaps,and the lipo was only 40% empty. So.. nice result :)
  
  Here's the detail story :  http://fangin.com/blog/2011/08/25/gopro-hero-external-lipo-power/

Also, I didn't know it had become that cheap to use a usb battery such as this one : http://www.amazon.fr/TeckNet-batterie-T%C3%A9l%C3%A9phones-Incredible-Blackberry/dp/B001AH0ITA/ref=sr_1_1?ie=UTF8&qid=1338902485&sr=8-1