Space officially begins according to "the man" at 100 km AGL, and is known as the Kármán line. Anything below that is not space, anything above that is space.
As the payload gets higher the temperature will drop, this is due to an affect called the adiabatic lapse rate. There is no absolute measurement for this as it is affected by moisture content in the air amongst other things, but it is defined by the International Civil Aviation Organisation As:
6.49°C Per kilometre altitude 3.560 Per 1000 feet in altitude
A glide ratio is the ratio between how far forward something will move and how far it will fall towards the earth at a given speed. For instance a glide ratio of three to one (3:1) means that for every 3 feet the vehicle moves forward in the sky, it drops 1 foot towards the Earth. I've massively oversimplified, but check out the links for a deeper slightly understanding.
This is going to be particularly important when we come to choosing the type, shape and size of parachute we want to use.
This website has another explanation of glide ratios in relation to parachutes, including a no wind day typical parachute will move forward 2000 feet for every 1000 feet it descends. Obviously the wind will play a part in this calculation.
- Typical parachute: 2:1
Given the coordinates:
Latitude: 53.718763 Longitude: -2.105415
How far can we drift either side of this point before we have to start the return to Earth.