Would the Lagrange points L4 and L5 of the Sun-Earth system make good locations for a pair of telescopes or does the likely debris around them present a hazard that outweighs the potential advantages?

I think this is roughly the state of play...

• The Lagrange L4 and L5 points have the potential advantage of providing instant parallax for a pair of space telescopes.

• Being stable, the L4 and L5 points are relatively easy to get to and cheap (in terms of fuel) to be stationed at.

• As a result of being stable, the L4 and L5 points also collect and retain some debris.

• There is some debris, including one known asteroid (2010 TK7) but the density of debris is currently unknown. It is slightly difficult to observe any current debris from the Earth since the L4/L5 points tend to be in the daytime sky.

• Missions to send probes to L4/L5 have been proposed but not yet organised. Such missions would probably allow us to evaluate the level of threat of collision and allow us to weigh the cost/benefit/risk of deploying a pair of space telescopes.

• Instant parallax is useful for observing relatively near objects, but much space telescope interest seems to be concerned with seeing distant objects, for which parallax is too small to be relevant.

• The L1 and L2 points, which we are using are unstable, so do not suffer from the debris issue, but have the advantage of low fuel requirement to stay on station.