Even though we are living in the era that it is no wonder we
imagine artificial objects traveling far away in the solar system, if letters
from the invisible objects come to hand regularly, it must make us feel something.
In fact, artificial objects, or explorers, in space just send us the curt letters
with rows of 2-digit value as originally designed. But sometimes we feel such
faithfulness commendable. Such illusion becomes a reality only if communication
with explorers is achieved.
Ears and eyes of explorers depend on the radio wave that can travel in the world
without air. They have kept in touch with earth by a sole means, the radio wave,
from long before the cellular phone diffuses in our society. In this way, communication
is literally a life rope for explorers once they are launched to space. This is
also true for us trying to make projects successful. When it comes to the loneliness,
there is nothing like space explorer traveling in space all on its lonesome? The
deep space communication is just like “listening attentively to lonely explorer’s
mumble.” Of course, our ears do not hear their mumble..
Development of transponder
Communication equipment aboard space explorers is called the transponder. This
is coined word, mixing up “transmitter” and “responder”. This
denotes equipment that returns answer for question. Everything called space vehicle
or satellite, not only explorer, carries the transponder. The reason why we, staying
on earth, can catch all events occurring in and around explorers in space is due
to the function of transponder. Needless to say, communication is possible only
if you have partner. The partner of transponder is transceiver located on the
ground, which acts as an interpreter for transponder’s language. If the theme
of this article is communication, we have to discuss both the transponder and
transceiver as a pair. But, since this article is about transponder, I don’t
mention the transceiver but ask you to keep it in mind that the transceiver is
always present on the ground.
The transponder is vital equipment for explorer and, accordingly, its history
is overlapped with the history of space development. As with many technologies
for explorer, transponder remains unchanged largely from its birth though it has
undergone research and development. At present, the transponder technology is
completed, being considered as a typical sample of reliability. In past, every
time scientific satellites/explorers were developed at the Institute of Space
and Astronautical Science (ISAS), transponders were also developed. Since any
challenge had its special and unique purpose in space science, specific specification
corresponding to the purpose was also requested for communication equipment. As
beautiful imagery of celestial bodies shows, the universe has a variety of figures.
So, it is natural that there is a variety of equipments.
Now, entering the 21st century, space science of ISAS takes a big step toward
the deep space. Following NOZOMI and HAYABUSA, new projects exploring the solar
system are proposed in rapid succession, taking down fence that the deep space
exploration is a special experiment. Taking up any project, its specialty must
be largely different from others. Under the circumstances, our conventional approach
that we advance step by step based on the past technology becomes not enough for
the new projects. Thus, the necessity to develop new transponder responding to
the deep space exploration is strongly recognized at ISAS toward the new era.