Major mission of the Explorer program - The Advanced Composition Explorer (ACE)

The Advanced Composition Explorer (ACE) is an Explorer mission that was managed by the Office of Space Science Mission and Payload Development Division of the National Aeronautics and Space Administration (NASA).

ACE launched on a McDonnell-Douglas Delta II 7920 launch vehicle on August 25, 1997 from the Kennedy Space Center in Florida.
The Earth is constantly bombarded with a stream of accelerated particles arriving not only from the Sun, but also from interstellar and galactic sources.

Study of these energetic particles contributes to our understanding of the formation and evolution of the solar system as well as the astrophysical processes involved. The Advanced Composition Explorer (ACE) spacecraft carrying six high-resolution sensors and three monitoring instruments samples low-energy particles of solar origin and high-energy galactic particles with a collecting power 10 to 1000 times greater than past experiments.
ACE orbits the L1 libration point which is a point of Earth-Sun gravitational equilibrium about 1.5 million km from Earth and 148.5 million km from the Sun. From its location at L1 ACE has a prime view of the solar wind, interplanetary magnetic field and higher energy particles accelerated by the Sun, as well as particles accelerated in the heliosphere and the galactic regions beyond.
ACE also provides near-real-time 24/7 continuous coverage of solar wind parameters and solar energetic particle intensities (space weather). When reporting space weather ACE provides an advance warning (about one hour) of geomagnetic storms that can overload power grids, disrupt communications on Earth, and present a hazard to astronauts.
The spacecraft has enough propellant on board to maintain an orbit at L1 until ~2024.

Galileo End of Mission

The Galileo spacecraft's 14-year odyssey came to an end on Sunday, Sept. 21, when the spacecraft passed into Jupiter's shadow then disintegrated in the planet's dense atmosphere at 11:57 a.m. Pacific Daylight Time. The Deep Space Network tracking station in Goldstone, Calif., received the last signal at 12:43:14 PDT. The delay is due to the time it takes for the signal to travel to Earth.

In the end, the Galileo spacecraft will get a taste of Jupiter before taking a final plunge into the planet's crushing atmosphere, ending the mission on Sunday, Sept. 21. The team expects the spacecraft to transmit a few hours of science data in real time leading up to impact.

UARS Mission

The satellite was launched in 1991 by the Space Shuttle Discovery. It is 35 feet long, 15 feet in diameter, weighs 13,000 pounds, and carries 10 instruments. UARS orbits at an altitude of 375 miles with an orbital inclination of 57 degrees. Designed to operate for three years, six of its ten instruments are still functioning. UARS measures ozone and chemical compounds found in the ozone layer which affect ozone chemistry and processes. UARS also measures winds and temperatures in the stratosphere as well as the energy input from the Sun. Together, these help define the role of the upper atmosphere in climate and climate variability.

The Apollo Missions

Forty years ago, men from Earth began for the first time to leave our home planet and journey to the moon. From 1968 to 1972, NASA's Apollo astronauts tested out new spacecraft and journeyed to uncharted destinations.

Apollo Missions started on May 25, 1961, when President John F. Kennedy announced the goal of sending astronauts to the moon before the end of the decade. Coming just three weeks after Mercury astronaut Alan Shepard became the first American in space, Kennedy's bold challenge set the nation on a journey unlike any before in human history.

Eight years of hard work by thousands of Americans came to fruition on July 20, 1969, when Apollo 11 commander Neil Armstrong stepped out of the lunar module and took "one small step" in the Sea of Tranquility, calling it "a giant leap for mankind."

Six of the missions (Apollos 11, 12, 14, 15, 16 and 17 ) went on to land on the moon, studying soil mechanics, meteoroids, seismic, heat flow, lunar ranging, magnetic fields and solar wind. Apollos 7 and 9 tested spacecraft in Earth orbit; Apollo 10 orbited the moon as the dress rehearsal for the first landing. An oxygen tank explosion forced Apollo 13 to scrub its landing, but the "can-do" problem solving of the crew and mission control turned the mission into a "successful failure."

Early Spaceflights of NASA- Mercury and Gemini

NASA's first high-profile program involving human spaceflight was Project Mercury, an effort to learn if humans could survive the rigors of spaceflight. On May 5, 1961, Alan B. Shepard Jr. became the first American to fly into space, when he rode his Mercury capsule on a 15-minute suborbital mission. John H. Glenn Jr. became the first U.S. astronaut to orbit the Earth on February 20, 1962. With six flights, Project Mercury achieved its goal of putting piloted spacecraft into Earth orbit and retrieving the astronauts safely.
Project Gemini built on Mercury's achievements and extended NASA's human spaceflight program to spacecraft built for two astronauts. Gemini's 10 flights also provided NASA scientists and engineers with more data on weightlessness, perfected reentry and splashdown procedures, and demonstrated rendezvous and docking in space. One of the highlights of the program occurred during Gemini 4, on June 3, 1965, when Edward H. White, Jr., became the first U.S. astronaut to conduct a spacewalk.