Over the past decades, we've
struggled to see beyond the atmosphere lying between earth and space.
Even from mountaintop observatories, the atmosphere has blurred
our view of the universe.
And because the atmosphere absorbs certain forms of energy,
our knowledge of celestial phenomena has been limited.
One answer has been to go beyond the atmosphere.
In fact, between the late sixties and the late seventies, NASA's launched
a series of special purpose observatories, revealing ultraviolet sources
such as very hot stars and very young stars.
These satellites made tremendous breakthroughs
and encouraged astronomers to move on to larger observatories
seeking answers about more distant galaxies,
mysterious pulsars and quasars.
And the universe itself.
Astronomers envision the next step a multipurpose observatory in space,
one that could image farther and more clearly than its predecessors,
uncovering phenomena in ultraviolet, visible
and infrared regions of the spectrum and observatory
that could expand our perception to the outer reaches of the universe.
That next step was HST.
NASA's Hubble Space Telescope.
With its precision optics and diverse array of scientific
instruments, NASA is responsible
for developing, operating and maintaining this ground size space observatory.
With its unparalleled goals,
the Hubble Space Telescope poses a much greater challenge to operate
than ground based observatories are the satellites
that came before it.
Led by NASA engineers, scientists and researchers
from universities, industries and the European Space Agency have
combined efforts to meet the challenge of operating Hubble Space Telescope.
The result is one of the most complex operations and maintenance systems
in the world one that ensures quality observations and spacecraft performance
into the next century.
To take a closer look, we started the Space
Telescope Science Institute in Baltimore, Maryland.
Aura, a consortium of American universities,
operates the Institute for NASA.
The Space Telescope Science Institute
is the International Center for Science Activities with HST.
It plans the day to day observations and sets up the long term science program.
Astronomers first come in contact with the institute
when they submit their proposed science program.
As with any major observatory, the demand for the telescope exceeds
the time available.
We expect to receive over 1000 proposals a year
and only 200 can be conducted.
A committee of international astronomers selects the proposals
based on their scientific merit.
Because the HST offers
several hundred instrument configurations, our scientists
work with the selected researchers to detail their observations.
Next, numerous proposals are incorporated into a week long observing schedule
that ensures the efficient use of every telescope minute.
There are many, many factors involved in scheduling observations
with the space telescope.
There are many instruments on board the space telescope.
Within the same instrument, there are several observing modes.
Even the simplest observation requires using different filters.
We may also have to revisit the same target at different times of the year.
We want to maximize the time spent observing with the space telescope
and minimize the time wasted moving the telescope around.
Therefore, we will group the observations to happen in the same area of the sky.
We also
want to use the same instrument for long periods of time, even weeks
at a time, to minimize switching instruments on
and off unnecessarily.
Before the telescope scheduled can be completed.
Another essential factor is entered the guide stars
to establish guide stars for operations.
The Institute has converted 1500 photographic plates of the sky
into a catalog of 15 million stars, using the catalog,
the institute's computer selects guide stars for each target.
HST stabilizes on a target by finding and locking onto
to guide stars with its precision guidance sensors.
The sensors detect any minor drift from the guide stars
and correct the spacecraft's position through the onboard computers
with the guide stars and other system factors incorporated.
The Institute produces a week long schedule which specifies
when, where and how HST science instruments will be used
from the institute.
The science schedule is transmitted to the Space Telescope Operations Control
Center, located at Goddard Space Flight Center in Greenbelt, Maryland.
This is the nerve center of HST ground system.
The science schedule automatically goes into one of the control center
computer systems, which adds commands for operating
and maintaining the observatory.
These new commands cover such operations as moving the telescope
or pointing its communications antennas.
The system also schedules links
to NASA's communication satellites
merging both the science and spacecraft commands.
The computer generates a master schedule for the week.
If this second by second schedule were printed out,
the stack would be 1 to 2 feet high.
Commands are sent to HST to onboard computers,
which on an average day carry out over 12,000 commands.
The spacecraft's
safety is also monitored as the control center.
A typical satellite has about a thousand parameters that must be monitored.
HST has about 6000.
These parameters include specific spacecraft temperatures, voltages,
electrical currents and the condition of its computers.
Our engineers must instantly recognize the codes for each
function, interpret their measurements, and take immediate action.
If something is unusual
because the engineers are overrun with data.
We became concerned about the potential for human error.
To minimize this possibility, we are developing an artificial
intelligence system that automates much of the analysis.
If the system finds something amiss, it tells the operator.
Eventually.
It will also prescribe a solution for the irregularity.
Before the actual observations begin.
Nasser must calibrate adjust his various systems
during a crucial seven month period following launch.
Marshall Space Flight Center, located in Huntsville,
Alabama, was responsible for building HST.
Early in the calibration process.
Marshall Personnel managed the spacecraft's initial checkout
from Goddard's control center.
At the beginning of deployment.
The shuttle bay doors open and the orbiter supplies power to HST.
Communication is then established between the ground control center
and the spacecraft to verify proper configuration
and to activate basic systems for thermal safety.
Next, the orbiter is arm lifts HST out of the bay
so the telescope's solar arrays and antennas can be extended.
The arm releases the observatory into orbit
some 300 miles above the earth.
HST Solar arrays are oriented properly
to convert the sun's energy into electrical power for the observatory.
The orbiter stays nearby for about two days after release.
In case HST needs further assistance during this early critical period,
once we establish that the spacecraft
can operate on its own, the orbiter returns to Earth.
Meanwhile, ground control engineers continue to verify that major components
are up and running and that the telescope is pointing properly.
Next, through a long series of calibrations, the telescope
mirrors, star trackers, bandgap sensors and rate gyros.
Our land at approximately the end of the first month.
Marshall officially turned responsibility for HST operations over to Garrett.
During the second month.
Goddard conducts further telescope
calibrations and early check out of the science instruments
subsequent check out of the optics and the instruments
occurs during the remaining five months.
Only then can the long awaited observations
begin
to make these observations.
HST commands must travel an intricate path.
The science commands from the Institute are integrated
with spacecraft commands at Goddard's Control Center.
Ultimately, the signals are relayed to NASA
tracking and data relay satellite orbiting 23.000 miles above Earth.
The commands then go into HST onboard computers to be implemented.
This path reverses when data gathered by an observation is sent back to Earth
with commands loaded into its computers.
The telescope automatically proceeds with observations.
In this case, HST pivots slowly to its new target.
Light from the target goes down the telescope and hits the primary mirror.
It reflects back to the secondary mirror, reduced to a narrow beam.
The light is aimed back to the focal plane just behind it.
The image is directed to HST is fine guidance sensors
which locate and lock on to guide stars on either side of the target.
With HST now centered on its target.
The light travels into the science instruments,
which will make the observation
the instruments shutters open.
The correct filter is selected and HST begins
its exposure.
While most observations are pre-planned, 10% require
real time interaction at the Institute by Scientists.
Real time observations with the Space Telescope Wi-Fi pre programing.
For example, we want to observe the red spots on Jupiter.
These are complicated operations because the planet moves and it also rotates.
In order to be able to do this, we have to take an early picture
of the planet, send information down to the ground,
and then have an operator make a very quick decision
as to exactly where the instrument that is being used has to be pointed.
This is a very challenging operation indeed.
Within
24 hours of an observation. the observer can obtain the data
from the Science Institute's Data Archive and Distribution Service.
The investigator who submitted the proposal has exclusive rights
to this information. For one year.
After this period, the data is available to scientists
around the world serving as an HST library.
The archive will distribute an equivalent of 500
million pages of information over a single year.
The observations are distributed through worldwide astronomical computer
networks are through optical disks,
magnetic tapes and photographs.
Astronomers can use this information at their home institute
to further their own research.
From this data, who can say what great discoveries will be made?
Astronomers hope for answers about black holes,
the evolution of galaxies and the size of our universe.
Looking to the future.
To ensure the continuous flow of such exciting data,
NASA has created contingency plans in contrast
to the unexpected repair of the Solar Maximum Mission spacecraft in 1984.
Massa has prepared for HST on orbit servicing.
HST is
designed and developed by NASA for on orbit servicing by astronauts.
Consequently, HST instruments and various components
were developed to be modular.
This allows the astronauts to replace degradable parts
such as solar arrays and batteries during routine servicing missions.
The modular design also makes it possible
to update the observatory with new instruments.
During the first planned maintenance mission for the HST.
We expect to remove one of the original scientific instruments
and replace it with a near infrared instrument.
The first scientific instruments on the HST are sensitive to the ultraviolet
and visible portions of the electromagnetic spectrum.
When we add an infrared capability, we will be able to examine regions
such as this, where stars are in the process of formation today
and will also be able to probe still further back into the early history
of our universe.
Hubble Space
Telescope operations can be compared with the complexity and challenge
of the operations necessary to send astronauts to the moon.
The expertize of thousands of individuals has contributed
to the innovative science instruments, computer systems, information systems
and maintenance hardware that constitute HST operations network.
This elaborate system supporting Hubble space Telescope promises long
sought answers to universal questions, exciting discoveries to ponder,
and possibly a new understanding of our universe.