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

Mercury-Redstone A Mercury-Redstone launches Freedom 7
and Alan Shepard on the first American manned suborbital
spaceflight. NASA
Mercury-Scout
On May 5, 1961, the same day the first American astronaut
was launched, NASA proposed using Scout rockets
to evaluate the Mercury tracking and real-time computer
network in preparation for manned orbital missions. The
proposal was approved, and on June 13, 1961, the NASA
Space Task Group issued detailed instrumentation requirements
for the modified Scout, which became known as
Mercury-Scout. Each Mercury-Scout was to carry a lightweight
communications payload into orbit to allow a
simulation of the tracking through the Mercury global
network of an actual Mercury capsule. Blue Scout II
number D-8 was modified for the first—and what would
turn out to be the only—Mercury-Scout mission, MS-1.
The launch was conducted by the U.S. Air Force, which
had already launched other Blue Scout rockets from
Cape Canaveral, on November 1, 1961. But 28 seconds
after liftoff, the rocket veered off course and had to be
destroyed by the range safety officer. Mercury program
Meteor 277
managers decided against further Mercury-Scout missions,
and by the end of 1961, Mercury-Atlas missions
MA-4 and MA-5 had demonstrated that actual orbiting
Mercury capsules could be successfully tracked.
mesosphere
A region of Earth’s atmosphere between 50 and 90 km
above the surface, where the temperature decreases with
altitude from a maximum of 7°C at the stratopause to a
minimum of −123°C at the mesopause.
MESSENGER (Mercury Surface, Space
Environment, Geochemistry and Ranging)
A NASA Discovery-class probe to investigate Mercury
from an orbit around the planet. Scheduled for launch in
March 2004, MESSENGER will make two flybys of Venus
and two of Mercury during a five-year voyage that will
fine-tune its trajectory through gravity-assists for Mercuryorbit
insertion in 2009. Once in orbit, MESSENGER
will have to contend with the intense heat in a region
where the Sun is up to 11 times brighter than on Earth.
However, sheltered behind a sunshield made of the same
ceramic material that protects parts of the Space Shuttle,
the probe’s instruments will be able to operate at room
temperature. Also, the spacecraft will pass only briefly
over the hottest parts of the planet’s surface, thereby limiting
the instruments’ exposure to reflected heat. During
its nominal one-Earth-year period of operation in orbit,
MESSENGER will analyze the planet with seven instruments,
including X-ray, gamma-ray, infrared, and neutron
spectrometers for exploring planetary composition,
a magnetometer to learn more about the magnetic field,
a laser altimeter for determining the height of surface features,
and a high-resolution camera. MESSENGER will
be designed, built, and operated by the Johns Hopkins
University Applied Physics Laboratory for NASA. The
only previous spacecraft to visit Mercury was Mariner 10
in 1974.
Meteor
Soviet weather satellites. The first Meteor system became
operational in 1969 after several years of testing. Subsequently,
about 30 Meteors were launched between 1969
and 1978 before the first of an upgraded version, Meteor
2, was orbited in July 1975. A further series, Meteor 3,
debuted in October 1985, although Meteor 2 satellites
continued to be launched in parallel. All of these spacecraft
were placed in high-inclination orbits because a geostationary
location—the usual norm for weather
satellites—provides a poor view of the high latitudes at
which much Russian territory lies. The Soviet Union did