Another "Space veteran" gets a mission extension, It appears as if Spitzer wil try and "hang in there" until JWST is in the commission phase.
Please pardon the shameless cut and paste approach, it's just that I'm not able to "one up" the quality of writing in the article so I don't try and improve it.
From,
http://www.nasa.gov/feature/jpl/spitzer-space-telescope-begins-beyond-phase
"Spitzer is operating well beyond the limits that were set for it at the beginning of the mission,"
said Michael Werner, the project scientist for Spitzer at NASA's Jet Propulsion Laboratory in
Pasadena, California. "We never envisioned operating 13 years after launch, and scientists are
making discoveries in areas of science we never imagined exploring with the spacecraft ."
NASA recently granted the spacecraft a two-and-a-half-year mission extension. This Beyond
phase of the Spitzer mission will explore a wide range of topics in astronomy and cosmology, as
well as planetary bodies in and out of our solar system.
Because of Spitzer's orbit and age, the Beyond phase presents a variety of new engineering
challenges. Spitzer trails Earth in its journey around the sun, but because the spacecraft
travels slower than Earth, the distance between Spitzer and Earth has widened over time. As
Spitzer gets farther away, its antenna must be pointed at higher angles toward the sun to
communicate with Earth, which means that parts of the spacecraft will experience more and
more heat. At the same time, Spitzer's solar panels point away from the sun and will receive
less sunlight, so the batteries will be under greater stress. To enable this riskier mode of
operations, the mission team will have to override some autonomous safety systems.
Spitzer, which launched on Aug. 25, 2003, has consistently adapted to new
scientific and engineering challenges during its mission, and the team expects
it will continue to do so during the "Beyond" phase, which begins Oct. 1.
The selected research proposals for the Beyond phase, also known as
Cycle 13, include a variety of objects that Spitzer wasn't originally planned
to address such as galaxies in the early universe, the black hole at the center of
Milky Way and exoplanets.
"We never even considered using Spitzer for studying exoplanets when it launched,"
Carey of NASA's Spitzer Science Center at Caltech in Pasadena. "It would have seemed
ludicrous back then, but now it's an important part of what Spitzer does."
Spitzer’s exoplanet exploration
Spitzer has many qualities that make it a valuable asset in exoplanet science,
including an extremely accurate star-targeting system and the ability to control
unwanted changes in temperature. Its stable environment and ability to observe
stars for long periods of time led to the first detection of light from known Lensing
Experiment (OGLE) were used together to find one of the most distant
exoplanets in 2005. More recently, Spitzer’s Infrared Array Camera (IRAC) has
been used for finding exoplanets using the "transit" method -- looking for a dip
in a star's brightness that corresponds to a planet passing in front of it. This
brightness that corresponds to a planet passing in front of it. This brightness
change needs to be measured with exquisite accuracy to detect exoplanets.
IRAC scientists have created a special type of observation to make such measurements,
using single pixels within the camera.
Another planet-finding technique that Spitzer uses, but was not designed for, is called
microlensing. When a star passes in front of another star, the gravity of the first star can
act as a lens, making the light from the more distant star appear brighter. Scientists are
using microlensing to look for a blip in that brightening, which could mean that the foreground
star has a planet orbiting it. Spitzer and the ground-based Polish Optical Gravitational
Lensing Experiment (OGLE) were used together to find one of the most distant planets known
outside the solar system, as reported in 2015. This type of investigation is made possible
by Spitzer’s increasing distance from Earth, and could not have been done early in the mission.
Peering into the early universe
Understanding the early universe is another area where Spitzer has broken ground. IRAC was
designed to detect remote galaxies roughly 12 billion light-years away -- so distant that their
light has been traveling for roughly 88 percent of the history of the universe. But now, thanks to
collaborations between Spitzer and NASA’s Hubble Space Telescope, scientists can peer even
further into the past. The farthest galaxy ever seen, GN-z11, was characterized in a 2016 study
using data from these telescopes. GN-z11 is about 13.4 billion light-years away, meaning its
light has been traveling since 400 million years after the big bang.
"When we designed the IRAC instrument, we didn't know those more distant galaxies existed,"
said Giovanni Fazio, principal investigator of IRAC, based at the Harvard Smithsonian Center
for Astrophysics in Cambridge, Massachusetts. "The combination of the Hubble Space
Telescope and Spitzer has been fantastic, with the telescopes working together to determine
their distance, stellar mass and age."
Closer to home, Spitzer advanced astronomers' understanding of Saturn when scientists using
the observatory discovered the planet's largest ring in 2009. Most of the material in this ring --
consisting of ice and dust -- begins 3.7 million miles (6 million kilometers) from Saturn and
extends about 7.4 million miles (12 million kilometers) beyond that. Though the ring doesn't
reflect much visible light, making it difficult for Earth-based telescopes to see, Spitzer could
detect the infrared glow from the cool dust.
The multiple phases of Spitzer
Spitzer reinvented itself in May 2009 with its warm mission, after the depletion of the liquid
helium coolant that was chilling its instruments since August 2003. At the conclusion of the
"cold mission," Spitzer’s Infrared Spectrograph and Multiband Imaging Photometer stopped
working, but two of the four cameras in IRAC persisted. Since then, the spacecraft has made
numerous discoveries despite operating in warmer conditions (which, at about minus 405
Fahrenheit or 30 Kelvin, is still cold by Earthly standards)
"With the IRAC team and the Spitzer Science Center team working together, we've really
learned how to operate the IRAC instrument better than we thought we could," Fazio said.
"The telescope is also very stable and in an excellent orbit for observing a large part
of the sky."
Spitzer's Beyond mission phase will last until the commissioning phase of NASA's James Webb
Space Telescope, currently planned to launch in October 2018. Spitzer is set to identify targets
that Webb can later observe more intensely.
