QUESTION:
Various questions as in answer!

ANSWER from Bill Ochs on 22 April, 1996:
Below are the answers pertaining to the new instruments being developed
for the 1997 and 1999 Servicing Missions.  If you have any others please
feel free to ask.

1. Do these instruments currently exist or do they have to be invented
yet?

For the 1997 Servicing Mission, we plan on installing two new science
instruments.  One is a camera to look at the near infrared portion of the
light spectrum and the other is an advance spectograph.  These
instruments have been in planning for many years and started production
about three years ago.  They are currently scheduled for delivery to the
Goddard Space Flight Center late this summer.

For the 1997 Servicing Mission, we are planning to install an advanced
camera up to 10 times better than the one we currently have.  Work on
this camera started last year and will be completed in 1998.

2. In order to install new instruments do others, already there, have to 
be removed?  If so, what happens to the tests they were performing?

The HST has 5 five slots for various instruments, which are always
filled.  So,  in order to put the new instruments in, the old instruments 
are removed and brought back by the Space Shuttle.  As far as the science
the old instruments were performing, in some cases the new instrument is a
n improvement over the old instrument and that particular type of science 
program continues, but with better results.  In other cases, the science 
program for that particuler old instrument may be over and the new 
instrument brings new capabilites to the HST for a new science program.

3. If it turns out, in 1997, that an instrument doesn't work right, as in 
the original mirror, do you have to wait until 1999 to fix it.

All our new science instruments udergo a very intensive testing program 
prior to the Servicing Mission, so the instrument should work once it is 
installed in the HST.  But if they was a problem, there are number of 
different options depending on the circumstances.  

Once the new instrument is installed in the HST and before the Space 
Shuttle goes home, each instrument will go through an electrical and 
critical function test.  If a failure is detected during this time frame, 
the first option will be to check the redundant side of the instrument.  
By redundant side I mean that each instrument contains two of everything, 
so that if a compoent fails there is a backup.  If the redundant side 
still fails, we will ask the astronauts to look at the instruments 
electrical connectors and if they find a problem, they have the tools to 
fix it on-orbit.  If the astronauts cannot find a problem, the new 
instrument will be taken out of the HST and the old one put back in.  The 
Space Shuttle will bring the new instrument home and it will be fixed and 
re-installed during the 1999 Servicing Mission.  

If a problem is found after the shuttle leaves, it would more than likely 
only limit the amount or types of science an instrument can do.  A 
decision would need to be made before the next Servicing Mission on 
whether to replace it or not.