The Hubble Space Telescope. Normal Size Image
IntroductionThe Hubble Space Telescope (HST) is NASA's flagship space observatory. From the beginning, it was decided to build into it features that allows it to be serviced while in space. By having astronauts regularly visit the observatory to repair and replace worn out components, the life of the telescope can be maximized. As a result of this capability, HST has a fairly large team of people that work on the project. There is a lot of work being done to continually design and build the next set of instruments that need to be installed.
My first involvement with HST started in 1996 when I joined the Solid State Recorder (SSR) Team. I designed and built the system that tests the Recorder on the ground while it is being built. HST uses it because it makes observations of the heavens nearly continuously, even though it is not able to get a data link to the ground at all times. While it is out of contact, the images are stored on the Recorder. Before the SSR was installed in 1997, HST used an actual magnetic tape recorder. This is because when HST was designed, that was proven and reliable. Nowadays computers and memory chips have advanced so much that computer memory can be used to store the images. The SSR represents a major improvement in performance. All those beautiful images that NASA releases from HST are possible because of the data storage of the SSR.
The Cartwheel Galaxy. Normal Size
I was present at the control center at NASA Goddard Space Flight Center (GSFC) when the SSR was installed in 1997. After the astronauts connected it up and it started working, they noticed something strange in the data that HST was sending to the ground about the newly installed SSR. After analyzing the data, we realized that it was being affected by cosmic radiation. SSR's advanced microcircuits is much more sensitive to this type of radiation that its predecessor, and this was somewhat of a surprise. Calculations had shown that the SSR should not have been this sensitive to radiation.
Installation of the SSR in 1997. Normal Size
SSR was not the only instrument affected. Another one called Advanced Camera System (ACS) was seeing the effects too. This was troubling to the upper managers at NASA, and the technical team was directed to prevent these surprises on the next mission to service HST. This next mission will take place in 2000, and we will be installing some more new advanced computer circuitry. Among the new components will be a completely new central computer for HST. This computer has to be rock-solid because problems could make the entire spacecraft useless.
The HOST MissionAs a result of these concerns, the HST Orbital Systems Test (HOST) Mission was created. Flying on the Shuttle Mission known as STS-95 in October 1998, it will give the instruments a ride into space for 10 days to evaluate their performance. In addition to the above mentioned concern for radiation, a problem has developed in one of the most important instruments on the telescope called NICMOS.
The HOST Mission Logo. Normal Size
NICMOS is an infrared instrument that takes pictures of the
of the universe. In order to take an effective image, the instrument
be very cold such that its own heat energy doesn't blind its detectors.
This is accomplished with a large block of solid nitrogen. Ordinarily
element is found on the earth as a gas, but it is kept so cold on HST
it is frozen as a block of nitrogen ice. This block is melting so fast
that the instrument, thought to be able to work until the year 2002,
run out of nitrogen ice at the end of 1998. Many of NASA's recent
including the one showing the existence of a planet beyond our solar
was made with NICMOS.
In order to save the instrument, NASA has decided to build a super refrigerator. This refrigerator will be able to cool to just 70 degrees above absolute zero. By connecting this cooler to NICMOS, we will be able to save the instrument. However, a cooler of this type has never flown in space. In order to prove that it will work in a zero gravity environment, a test flight of the cooler will be needed.
The following instruments will be flown on the HOST mission. These are all instruments scheduled to be installed into HST in the year 2000:
- The new HST computer, known as the 486.
- Another Solid State Recorder.
- The NICMOS cooler, mentioned above.
- A radiation measurement sensor to find out the radiation level.
- A vibration sensor to see how noisy or quiet the cooler is.
- A computer that will control all of the above instruments and components.
The HOST carrier. Normal Size
The carrier is shown in the picture above. Also known as the
this is the structure that is placed into the shuttle for the mission.
Its "C" shape reflects the shape of the shuttle cargo bay. The large
rectangle at the top is the radiator that gets rid of the heat
by the cooler. The blue box on the right is the 486 computer, and the
two black boxes are the NICMOS cooler. The entire cradle is pictured
in a blue holding fixture. This blue fixture is left behind when the
is lifted into the shuttle.
Building the HOST ControllerThe HOST Controller is the central computer for the HOST mission. It operates the installed instruments just as if they were on HST, and communicates their status to the ground. In essence the HC makes the instruments believe they are still connected to HST in order to monitor their operation. There will be a command center at Kennedy Space Center during the mission where commands can be sent to the Controller to operate the instruments.
Host Controller during assembly. Normal size
The Controller was conceived, designed, tested and delivered
9 months. Costing only $1.6 million, its low cost and quick delivery
only be possible with a small team and aggressive planning. As a
I was given free reign and ran the project technically . It was very
and fun to build the computer and they delivered with only a few days
spare for me to be able to go back to Aruba for a vacation and to view
the big solar eclipse of Feb. 1998.
Some technical details:the complexity of the HC comes from its many interfaces that mimic existing HST connections and new interfaces not used on HST. The following interfaces are incorporated:
- 1553 Electrical communication interface.
- 1773 Optical communication interface.
- EIA-422 Serial Data interface.
- RIU Serial Digital. An HST Serial bus.
- DIU Serial Digital. Another HST Serial bus.
- DIU relay driver for relay control.
- DMU data and control bus. An HST communication bus.
Host Controller during Environmental test.
From left to right, Dave Southwick, Edward Cheung, Roger Chiei. Normal size
Building a project for space means a level of testing that would break normal electronics. We first put the Controller into a sealed chamber called the Thermal-Vac chamber and pumped all the air out of it. This simulates the vacuum environment of space. Next the temperature in the chamber was varied from cold to hot to simulate the temperature extremes of space. These temperatures can vary from +40 C in the sun to -90 C when facing deep space.
Host Controller during tests in the vibration facility.
From left to right, Kevin Hughes, Edward Cheung,
Steve Horowitz, Roger Chiei. Normal size
Next we continued the testing by bolting the Controller onto a shaker that simulates the violence of launch. The Controller was shaken so hard that it acts as a speaker, filling the room with such loud sound that you must wear ear protection.
HOST Controller, mounted on flight HOST cradle. Normal size
Finally, the Controller was delivered to the HOST cradle, where it was installed and tested. After that the other instruments were installed over the course of the months that followed. The cradle itself then underwent its own tests. This included placing it into a huge chamber (the size of a house) for vacuum and temperature tests, and vibration testing. The cradle vibration test consists of rolling it into a large sealed room that is then flooded by a roaring sound to simulate the launch conditions. This sound is so loud that it is just like standing next to the Shuttle engines.
Complete HOST cradle. Normal size
HOST Cradle being lifted into the Thermal-Vac chamber for vacuum and
temperature tests. The HOST Controller is visible as the silver box on
the right bottom side of the cradle (marked HC). Normal size
Some Candid Shots during Controller development:
- John Allen, the software lead on Controller
- Angela Cuellar, NICMOS hardware engineer
- The Software Lab at DSC
- Problem Solving Session at DSC
Preparations for STS-95
Meeting Curt Brown, the commander of STS-95, Normal size
For the mission I will be working at a console at the Kennedy Space Center instead of at the Goddard Space Flight Center. We will be communicating and controlling the instruments directly. As a result of this work, I needed special training to work safely in that environment. For example, due to the many hazardous material present at the launch facility, special training with breathing apparatus is needed.
During ELSA (Emergency Life Support Air) Training.
This type of training is needed to work near the launch pads at Kennedy.
This particular pack (yellow) allows for 10 minutes of air. Normal size
Arrival at the Kennedy Space Center (KSC)The HOST cradle was transported down to KSC on a large enclosed and air conditioned container on 25 August 1998. After arrival, it was housed in the Space Station Processing Facility (SSPF) in the stand shown below. This facility mimics the Shuttle electrically and mechanically and verifies that the hardware will fit and talk to the Shuttle properly when it is installed at the launch pad.
The HOST Cradle at KSC as shot by one of the
live web cameras. The cradle is the orange object in the middle.
This facility mimics the shuttle mechanically and electrically.
This picture was shot on September 15 (258th day) at 8:46 am.
This corresponds to 12:46 GMT time.
The tests on the cradle that were performed back home at Goddard were repeated at the SSPF to make sure the trip to Florida was successful. Here is also the first time that the HOST Controller communicated to a 'real' Space Shuttle. Before this event we had been using a commercial system to mimic the Shuttle. Fortunately, all the tests were successful, allowing the transfer of the cradle into the container that will be its transportation to the launch pad.
This is the canister that transported the cradle to the launch pad. Full Size
Transfer of the cradle from the SSPF stand into the canister.
The live web camera is fastened to the wall that is the background in the bottom set of images.
It is barely visible thru the 'hole' in the cradle in the top right image.
The cradle installed into the canister. The word 'AFT' is the
wall of the canister representing the 'back' of the orbiter.
This image shot from the PCR.
After the installation of the HOST cradle on September 23 1998, the canister's doors are closed. The canister is then rotated upright into a vertical orientation, and then installed onto the launch pad. There the payloads are first transferred into the launch pad and then into Shuttle.