Mission Overview
================

Mariner 10 was the seventh successful launch in the Mariner series
and the first spacecraft to use the gravitational pull of one planet
(Venus) to reach another (Mercury). The spacecraft flew by Mercury
three times in a heliocentric orbit and returned images and data on
the planet. Mariner 10 is the only spacecraft to have visited
Mercury.

Spacecraft and Subsystems

The spacecraft structure was an eight-sided framework with eight
electronics compartments. It measured 1.39 m diagonally and 0.457 m
in depth. Two solar panels, each 2.7 m long and 0.97 m wide, were
attached at the top, supporting 5.1 sq m of solar cell area. The
rocket engine was liquid-fueled, with two sets of reaction jets used
to stabilize the spacecraft on three axes. It carried a low-gain
omnidirectional antenna, composed of a honeycomb-disk parabolic
reflector, 1.37 m in diameter, with focal length 55 cm. Feeds
enabled the spacecraft to transmit at S- and X-band frequencies. The
spacecraft carried a Canopus star tracker, located on the upper ring
structure of the octagonal satellite, and acquisition sun sensors on
the tips of the solar panels. The interior of the spacecraft was
insulated with multiplayer thermal blankets at top and bottom. A
sunshade was deployed after launch to protect the spacecraft on the
solar-oriented side.

Instruments on-board the spacecraft measured the atmospheric,
surface, and physical characteristics of Mercury and Venus.
Experiments included television photography, magnetic field, plasma,
infrared radiometry, ultraviolet spectroscopy, and radio science
detectors. An experimental X-band, high-frequency transmitter was
flown for the first time on this spacecraft.

Mission Profile

Mariner 10 was placed in a parking orbit after launch for
approximately 25 minutes, then placed in orbit around the Sun en
route to Venus. The orbit direction was opposite to the motion of
the Earth around the Sun. Mid-course corrections were made. The
spacecraft passed Venus on February 5, 1974, at a distance of 4200
km. It crossed the orbit of Mercury on March 29, 1974, at 2046 UT,
at a distance of about 703 km from the surface. The TV and UV
experiments were turned on the comet Kohoutek while the spacecraft
was on the way to Venus. A second encounter with Mercury, when more
photographs were taken, occurred on September 21, 1974, at an
altitude of about 47,000 km. A third and last Mercury encounter at
an altitude of 327 km, with additional photography of about 300
photographs and magnetic field measurements occurred on March 16,
1975. Engineering tests were continued until March 24, 1975, when
the supply of attitude-control gas was depleted and the mission was
terminated.

Total research, deployment, launch, and support costs for the
Mariner series of spacecraft (Mariners 1 through 10) was
approximately $554 million.


Mission Phases
==============

EARTH VENUS CRUISE
------------------
The Earth-Venus cruise period is defined as spanning the time
between launch and 3 days before Venus closest approach.

Spacecraft Id : M10
Target Name : SOLAR WIND
Mission Phase Start Time : 1973-11-03
Mission Phase Stop Time : 1974-02-01T23:59:59.999Z

VENUS ENCOUNTER
---------------
The Venus encounter period is defined as spanning 6 days about
Venus closest approach. Closest approach to Venus occurred at
1974-02-05 17:01:50 UT.

Spacecraft Id : M10
Target Name : VENUS
Mission Phase Start Time : 1974-02-02T00:00:00.000Z
Mission Phase Stop Time : 1974-02-08T23:59:59.999Z

VENUS MERCURY CRUISE
--------------------
The Venus-Mercury cruise period is defined as spanning the time
between 3 days after Venus encouter and 3 days before Mercury
closest approach.

Spacecraft Id : M10
Target Name : SOLAR WIND
Mission Phase Start Time : 1974-02-09T00:00:00.000Z
Mission Phase Stop Time : 1974-03-26T23:59:59.999Z

MERCURY ENCOUNTER I
-------------------
The first Mercury encounter period is defined as spanning 6 days
about Mercury closest approach. Closest approach to Mercury
occurred 1974-03-29 20:46:38 UT at an altitude of 703 km.

Spacecraft Id : M10
Target Name : MERCURY
Mission Phase Start Time : 1974-03-27T00:00:00.000Z
Mission Phase Stop Time : 1974-04-02T23:59:59.999Z

MERCURY MERCURY CRUISE I
------------------------
The Mercury-Mercury cruise period is defined as spanning the time
between 3 days before Mercury Encounter I and 3 days before
Mercury Encounter II.

Spacecraft Id : M10
Target Name : SOLAR WIND
Mission Phase Start Time : 1974-04-03T00:00:00.000Z
Mission Phase Stop Time : 1974-09-17T23:59:59.999Z

MERCURY ENCOUNTER II
--------------------
The second Mercury encounter period is defined as spanning 6 days
about Mercury closest approach. Closest approach occurred
1974-09-21 21:59:00 at an altitude of 47,000 km.

Spacecraft Id : M10
Target Name : MERCURY
Mission Phase Start Time : 1974-09-18T00:00:00.000Z
Mission Phase Stop Time : 1974-09-24T23:59:59.999Z

MERCURY MERCURY CRUISE II
-------------------------
The Mercury-Mercury cruise period is defined as spanning the time
between 3 days before Mercury Encounter II and 3 days before
Mercury Encounter III.

Spacecraft Id : M10
Target Name : SOLAR WIND
Mission Phase Start Time : 1974-09-25T00:00:00.000Z
Mission Phase Stop Time : 1975-03-12T23:59:59.999Z

MERCURY ENCOUNTER III
---------------------
The third and last Mercury encounter period is defined as spanning
6 days about Mercury closest approcah. Closest approach occurred
1975-03-16 22:39:23 at an altitude of 327 km.

Spacecraft Id : M10
Target Name : MERCURY
Mission Phase Start Time : 1975-03-13T00:00:00.000Z
Mission Phase Stop Time : 1975-03-19T23:59:59.999Z

END OF MISSION CRUISE
---------------------
The end of mission cruise period is defined as spanning the time
between 3 days after Mercury Encounter III and when the mission
was terminated.

Spacecraft Id : M10
Target Name : SOLAR WIND
Mission Phase Start Time : 1975-03-20T00:00:00.000Z
Mission Phase Stop Time : 1975-03-24T23:59:59.999Z

References
==========

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