Question

find out how,when a space voyage is planned how space debris has to be taken into consideration

Answer 1

When a space voyage is planned space debris has to be taken into consideration. Space debris is the collection of defunct man - made objects in space. It consists of old satellites, spent rocket stages, and fragments from disintegration, erosion, and collisions. This junk in space poses a threat to the future of spaceflight and also the environment. NASA and other space practitioners try to manage the threats posed by existing orbital debris and minimize the potential for new debris. They are devising better ways to track and identify space debris and have developed scavenging concepts like fishing nets, lasers and garbage scows.

Answer 2

Space orbital debris are objects in space that are not useful any longer and are as a result of the man-made structures to space.
Since collision of the debris with a space-ship or a space station can result to damage to these spacecrafts or the loss of life, serious measures are undertaken to ensure that collisions with the space debris do not occur.
NASA's long standing space guidelines are being used to ensure that collision of spacecrafts and the debris do not occur. The guidelines involve the drawing of an imaginary box around the spacecraft which is used to predict collision probability with debris using computer programs. 
If such collisions are predicted to have high probability according to the guidelines, special maneuvers are made to avoid the collision. This involves mission controls in ground stations such as those in Moscow and Huston, Texas.