Why are more instruments added to the Hubble space telescope rather then being sent into orbit separately?

Question

i also want to know what might be the advanige of each alternative. this is for grade 9 science

Answer 1

1. To work with the telescope and give it more options like a wider spectral view.
2. To improve the existing telescope and repair flaws in it.
3. To share the same power and structure of the telescope making it cheaper than a totally new satellite.
4. To share the same orbit, putting fewer satellites in orbit.
5. To ride in the safer and more reliable Space Shuttle instead of a dangerous ride on a delta rocket or with a Pegasus booster.