The name of an old sci-fi movie

[Jack McSlay]

Can anyone help? I'm trying to find out the name of this old movie I've seen once

It's apparently a `70s or `60s movie where astronomers had seemingly found a planet with identical conditions to earth, and they sent a ship with tow astronauts to investigate the possibility of colonization. A system failure occurs and they crash land on the planet.
One of the astrunauts die and the other survives, and it seems as if they had just returned to earth, even tho the trip had apparently been successful. later he discovers he actually landed on an planet identical to earth, except for the fact the entire planet is a mirrored version of earth itself.
They then try to send him back to his original earth but yet another malfunction causes the ship to crash-land back into mirrored earth, this time falling back into the launch site, blowing up and killing almost everyone. Then the movie ends with one survivor (possibly the only one), now aged, attempting suicide by running towards a mirror in his wheelchair.

[Dekari]

I think your looking for Doppelgänger