The Complete Book of Spaceflight: From Apollo 1 to Zero Gravity

operating lifetime of 12 years, and the more advanced,
160-kg Nova, with an average lifetime of nine years. The
last Transit satellite launch was in August 1988. Day-today
operations, including telemetry, tracking, and control,
were conducted by the Naval Space Operations
Center at Point Mugu, California, while the Applied
Physics Laboratory at Johns Hopkins University devised
and designed all aspects of the satellites.
translation
The motion of a spacecraft along its principal axis.
translational thrust
The thrust needed to propel a missile or space vehicle
from one given position to another.
translunar
A term commonly used in referring to the phase of flight
from Earth orbit to lunar orbit. Most reference books,
however, describe translunar as referring to space outside
the Moon’s orbit around the Earth, while cislunar refers
to space between the Earth and the Moon’s orbit.
transonic
Flight in the range between the onset of compressibility
effects (a Mach number of 0.7) and the establishment
of fully supersonic flight conditions (a Mach
number of 1.4).
transponder
A radio or radar system that is triggered by a received signal.
Transponders are important components of communications
satellites and consist of a receiver, a frequency
converter, and a transmitter package. They have a typical
output of 5 to 10 watts and operate over a 36 to 72 MHz
bandwidth in the L-, C-, Ku-, or Ka-band, except for
mobile satellite communications. Communications satellites
typically have 12 to 24 onboard transponders,
although the Intelsat 904, at the extreme end, has 98 (76
C-band and 22 Ku-band).
transporter/launcher
A transportable launcher that supports an integral umbilical
tower and an erect space vehicle. It usually consists of
the transporter (crawler) unit and the launcher (platform)
vehicle.
transverse acceleration
The inertial force produced by an acceleration acting
across the body, perpendicular to the long axis of the
body, as in a chest-to-back direction.
TRMM (Tropical Rainfall Measuring Mission) 445
trapped propellant
In a liquid-fuel rocket engine, the amount of fuel left in
the tanks that cannot be used because of the suction limitations
of the pumping systems.
Triana
An Earth observation satellite that is part of NASA’s
Earth Probe program. After reaching a halo orbit at the
first Lagrangian point in the Earth-Sun system, Triana
will transmit full-color images of the entire sunlit side of
Earth once every 15 minutes. These images, which will be
distributed continuously over the Internet, will highlight
global vegetation structure, cloud and ozone cover, and
atmospheric aerosol thickness, and provide a better
understanding of how solar radiation affects Earth’s climate.
Named after Rodrigo de Triana, the first person to
see the New World from Columbus’s ship, Triana is
being developed at the Scripps Institution of Oceanography,
San Diego. No date has yet been set for the spacecraft’s
launch.
TRMM (Tropical Rainfall Measuring Mission)
A joint NASDA (Japan’s National Space Development
Agency) and NASA Goddard Space Flight Center mission
dedicated to measuring tropical and subtropical
rainfall, an important but poorly understood factor
affecting global climate. TRMM, one of the first spacecraft
in NASA’s EOS (Earth Observing System), returns
long-term data on rainfall and energy budget measurements,
which will be used to better understand global climate
changes and their mechanisms. The large spatial
and temporal variations in tropical rain make it difficult
to measure from Earth’s surface, and TRMM provides
measurement accuracies possible only from an orbiting
platform. The satellite and four instruments are provided
by the United States, while Japan has supplied one
instrument and launch services. The scientific payload
includes: Clouds and the Earth’s Radiant Energy System
(CERES), a passive broadband scanning radiometer with
three spectral bands (visible through infared) that measures
Earth’s radiation budget and atmospheric radiation
from the top of the atmosphere to the planet’s surface;
Lightning Imaging Sensor (LIS), an optical telescope and
filter imaging system that investigates the distribution
and variability of both intracloud and cloud-to-ground
lightning; Precipitation Radar (PR), the first spaceborne
Launch
Date: November 27, 1997
Vehicle: H-2
Site: Tanegashima
Orbit: 344 × 347 km × 35.0°