Key Questions We Want to Answer:
goal of RACE is to place a rubidium atomic clock in orbit.
This clock will be used to perform a
series of experiments to test Einstein's Theory of Relativity,
and as well will advance the state of clock science into
a new frontier. The RACE clock will keep time so well that
if it ran for three billion years it would lose less than
1 second! Future clocks based on the technology developed
for RACE might be used to coordinate all of the world's
clocks, as well as for and telecommunications, and navigation-both
on Earth and in space.
What We Already Know:
RACE will build on the technology of the PARCS clock experiment
that will fly two years previously, using advanced shutters
similar to those developed for PARCS, and laser cooling
techniques to produce ultra-cold atoms with a temperature
of just one-millionth of degree above absolute zero. However,
RACE will introduce several new features that will allow
it to achieve its unprecedented accuracy. First it will
employ rubidium atoms rather than cesium, because this largely
eliminates a major source of error in laser-cooled clocks,
namely a frequency shift that arises due to collisions between
atoms within the clock. It will also use a novel "two
clocks in one" configuration featuring two back-to-back
sets of clock cavities, with a source of ultra-cold atoms
between them. The RACE design allows for the reduction of several
other sources of error, including those induced by vibrations
of the satellite.
What We Hope to Find Out:
One of the many relativity experiments that we would like to
do involves a comparison of the RACE clock with another clock,
perhaps one like SUMO.
The SUMO clock keeps time by measuring
how long it takes for microwaves to bounce back and forth
within the extremely reflective surfaces of a superconducting
cavity (for more information, see SUMO experiment). If we
can compare the clocks at different parts of the satellites'
orbit, we can test whether the speed of microwaves (which
is the same as the speed of light, since both are forms
of electromagnetic waves) is the same for all parts of the orbit,
regardless of their orientation or velocity. This experimental
test of a relativity prediction can be performed a million
times better than ever before.
We'll Conduct Our Experiment:
Laser pulses sent by a ground station
will be used to compare the time kept by a ground clock
with that of the clock in orbit.
Closely related experiments:
Additional Information: See the SUMO
The Principle Investigator for RACE is at Yale University.