|
+ Play
Audio
|
+ Download Audio | +
Email to a friend | +
Join mailing list
October
4, 2007: "Beep… beep… beep...."
That's the sound that marked the beginning of the Space Age
fifty years ago. It was a simple radio tone transmitted by
the first satellite, Sputnik 1, as it orbited Earth in October
1957.
 Since
then communication with spacecraft has advanced tremendously.
Yet a modern probe on the way to the edge of the solar system
is using Sputnik-like tones to send messages back to Earth.
Right:
In Oct. 1957, ham radio operator Roy Welch of Dallas, Texas,
tunes in to the 20 MHz radio tones of Sputnik. [More]
[Larger image]
Why
the retro technology? It solves a modern problem: multiplication.
Sputnik has so many descendants! There are robots on Mars;
spacecraft circling Saturn, Mars and the Sun; probes en route
to Mercury, the asteroid belt and even Pluto. All of these
missions are trying to talk to Earth, creating a cacophony
that threatens to overtax NASA's Deep Space Network. If only
these probes could learn to communicate with greater brevity
as Sputnik once did.
Enter
Beacon Monitor--a device onboard NASA's New Horizons spacecraft
that communicates with Earth using only eight simple tones.
It leverages the fact that New Horizons doesn't have much to
do during its 9-year voyage to Pluto other than report its status
to Earth. "I'm okay," sums up a typical weekly transmission.
New
Horizons is capable of complex communication. It can transmit
detailed images and data streams rich in numerical information.
"But when we only need a basic status check, a few simple
tones are fine," says Henry Hotz an engineer at NASA's
Jet Propulsion Laboratory who helped develop the technology.
Despite
its seeming simplicity, the beacon is sophisticated. New Horizons
has many systems and all of them must be checked. Onboard
software boils down the entire situation into a succinct "diagnosis."
The system then uses a low-power antenna to transmit the diagnosis
as one of eight simple radio tones. One means I'm okay
while the other seven signify calls for help ranging in urgency
from Help me soon to Help me now to Red
Alert! I'm in big trouble.
Above: Sputnik (left) and New Horizons (right).
This
approach has many advantages. "Simple tones from a distant
probe are much easier to detect on Earth than an ordinary
data transmission," explains Hotz. "If you miss
part of a complex data stream the information is lost, but
any part of a simple tone can tell you its frequency, thus
revealing the message." The simpler transmission means
that the beacon can use less of the probe's limited power
(New Horizons operates on less power than a pair of 100-watt
household light bulbs), and mission scientists can use smaller
dishes to receive the signal. "Both of these advantages
cut costs and make a mission more feasible."
Beacon
Monitor was first tested onboard Deep Space 1, an experimental
spacecraft flown in 1998 by NASA's New Millennium Program.
The raison d’etre of Deep Space 1 was to test a suite
of cutting-edge technologies (e.g., an ion engine, a smart
autopilot, super-solar arrays and a back-to-the-future status
monitor) for possible use on future missions. "Beacon
Monitor passed with flying colors and was later installed
on New Horizons."
So,
as the Space Age began, it continues, to Pluto and beyond.
Close your eyes. Can you hear the tones?
SEND
THIS STORY TO A FRIEND
Authors: Dr.
Tony Phillips, Patrick Barry | Production Editor:
Dr. Tony Phillips | Credit: Science@NASA
|
