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

eccentricity
A measure of the elongation of an orbit; specifically, the
distance between the foci of an ellipse divided by the
major axis. The eccentricity of closed orbits varies from 0,
for a perfect circle, to almost 1, for an extremely flattened
ellipse. Open orbits have eccentricites of 1 (parabolic) or
greater (hyperbolic).
Echo
The world’s first passive communications satellites.
Each Echo spacecraft was a large aluminized Mylar balloon
inflated in orbit, which provided a reflective surface
so that two-way voice signals could be bounced from
ground stations on the west and east coasts of the United
States. Following the failure of the launch vehicle carrying
Echo 1, Echo 1A (commonly referred to as Echo 1)
was placed in orbit and used to redirect transcontinental
and intercontinental telephone, radio, and television signals.
Its success proved that microwave transmission to
and from satellites in space was possible and demonstrated
the promise of communications satellites. Also,
because of its large area-to-mass ratio, it provided data for
the calculation of atmospheric density and solar pressure.
With a diameter of 30.5 m, Echo 1A was visible to the
unaided eye over most of the Earth and brighter than
most stars. The 41.1-m-diameter Echo 2—the first joint
American/Soviet collaboration in space—continued the
passive communications experiments, enabled an investigation
of the dynamics of large spacecraft, and was used
for global geometric geodesy. Although NASA abandoned
passive communications systems in favor of active
satellites following Echo 2, the Echo program demonstrated
several ground station and tracking technologies
that would be used by active systems. (See table, “Echo
Satellites.”)
EchoStar
A constellation of direct broadcasting satellites in geosynchronous
orbit operated by EchoStar Orbital Corporation.
The seventh EchoStar was launched on February
21, 2002; EchoStar 8 was scheduled for liftoff in mid-
2002.
Echo Satellites
Eddington 115
ecliptic
The plane in which Earth moves around the Sun.
ecological system
A habitable environment either created artificially, such
as in a space colony, or occurring naturally, such as the
environment on Earth, in which man, animals, and other
organisms live in mutual relationship with one another.
ECS (European Space Agency
Communications Satellites)
A series of satellites launched in the 1980s to support
European telecommunication services, including telephone,
telex, data, and television.
ECS (Experimental Communications Satellite)
Two Japanese satellites, also known by the national name
of Ayama (“expansion”), launched by NASDA (National
Space Development Agency) to carry out millimeterwave
communications experiments. Both failed—ECS
because the third stage of the N-1 launch vehicle came in
contact with the satellite after separation, and ECS-B
because of a fault with the apogee kick motor.
ECS and ECS-B
Launch
Date: February 6, 1979 (ECS); February 22, 1980
(ECS-B)
Vehicle: N-1
Site: Tanegashima
Size: 1.4-m diameter cylinder
Mass: 130 kg
Eddington
An ESA (European Space Agency) mission to detect seismic
vibrations in the surfaces of stars and to search for
Earth-like extrasolar planets using precise photometry
(light-intensity measurements). Named in honor of the
English astrophysicist Arthur Stanley Eddington (1882–
1944), it is expected to be launched after 2008, probably
by a Soyuz-Fregat rocket from Baikonur. Eddington will
Spacecraft Date
Launch
Vehicle Site Orbit Mass (kg)
Echo 1 May 13, 1960 Delta Cape Canaveral Failed to reach orbit 56
Echo 1A Aug. 12, 1960 Delta Cape Canaveral 966 × 2,157 km × 47.3° 76
Echo 2 Jan. 25, 1964 Thor-Agena B Vandenberg 1,030 × 1,315 km × 81.5° 256