PLATO is a European Space Agency telescope also called as
Europe's Planet-Hunting Telescope. It is expected
to launch in 2024. The name stands for "PLAnetary Transits and
Oscillations of stars." The goal of this mission is to figure out under
what conditions planets form and whether those conditions are favorable for
life.
To do this, PLATO will seek out and investigate Earth-size
exoplanets, especially planets that orbit in the habitable zone around sun-like
stars. (The habitable zone is usually defined as the area around a star where
there is enough energy for liquid water on a planet's surface, although
habitability also depends on other factors such as star variability.) It will
determine how big their radii are; verify the mass of the planets from
ground-based observatories; use astroseismology or "starquakes" to
learn about a star's mass, radius and age; and identify bright targets for atmospheric
spectroscopy along with other telescopes. If all goes to plan, the mission
should be able to provide detailed information on hundreds of rocky and giant
planets, providing more information about how solar systems form generally.
PLATO's primary mission is expected to last four years.
However, the telescope is designed to last 6.5 years and its consumables, such
as fuel, are expected to last about eight years. This means that the telescope
could continue operations if its science mission was extended.
PLATO history
PLATO, which is named after the Ancient Greek philosopher
Plato, was first proposed in 2007 after ESA put out a call for its Cosmic
Vision 2015–2025 program. Cosmic Vision is the name of the current phase of
ESA's long-term space science missions.
ESA, like NASA, solicits opinions from the science community
(ahead of selecting missions) to see what areas of space should be studied
next. ESA then puts out calls for missions for a launch opportunity, attracting
competitors that must present their science case.
PLATO was first proposed in 2007 as a part of Cosmic
Visions, finishing assessment and definition phases in 2009 and 2010,
respectively. ESA then put out a call in 2010 for a medium-class mission launch
opportunity.
PLATO, as well as two other missions — Solar Orbiter and
Euclid (a mission to investigate dark energy and dark matter) —were selected as
the finalists for this competition. Subsequently, Solar Orbiter was chosen for
a 2017 launch date and Euclid for a 2020 launch date.
In February 2011, PLATO went up against four other
medium-class mission candidates for a 2024 launch date. The others were EChO
(the Exoplanet CHaracterization Observatory), LOFT (the Large Observatory For
X-ray Timing), MarcoPolo-R (to collect and return a sample from a near-Earth
asteroid) and STE-Quest (Space-Time Explorer and QUantum Equivalence principle
Space Test).
PLATO was selected in 2014 for the launch opportunity, which
is also called M3 (for the third medium-class mission under Cosmic Visions.)
The spacecraft is now in its design phase, which will take several years before
it is finalized for construction.
PLATO science
The spacecraft will be launched from Earth on a Soyuz-Fregat
rocket bound for a location called a Lagrange point. A Lagrange point is a
relatively stable gravitational zone in space. PLATO will specifically be
targeted for the L2 Lagrange point, a spot in space on the "dark"
side of the Earth (meaning that the sun is always in the opposite
direction.)
L2 has been used before for the Wilkinson Microwave
Anisotropy Probe (WMAP) and Planck spacecraft, and is also the region where
the James Webb Space Telescope will operate. Since L2 is relatively
unstable, the spacecraft will follow a Lissajous orbit, which is a path around
the Lagrange point, and periodically use fuel to stay in a consistent orbit.
The payload and science are contributed by a PLATO mission
consortium (funded by European national funding agencies) while ESA provides
the spacecraft, the CCDs, mission operations and part of the science
operations.
PLATO's goal is to watch a large sample of bright stars for
months or years, and measure them to high precision. By watching the stars for
long periods, PLATO will be able to discern the light curve of the star, or the
variations in its light transmitted over time.
Since PLATO will last four years (at the least), the primary
science mission will have it observe two regions of the sky for two years each.
It's possible, however, that the telescope could instead do one long-duration
observation of three years, and then move around in the sky for the fourth year
of its primary science mission.
"In view of the exceptionally fast development of
exoplanet science, the final observing strategy will be investigated throughout
the mission development and decided two years before launch," ESA
said.
The long-term goal of many planetary observers is to find
planets like Earth, and to seek signs of habitability on those other planets.
While examining the atmospheres of these tiny planets will require a more
advanced observatory, knowing where they are is a first step.
Other space observatories looking for Earth-like planets
include Kepler Space Telescope (in operation since 2009), the
forthcoming Transiting Exoplanet Survey Satellite (TESS) and to a lesser
extent, the forthcoming James Webb Space Telescope (JWST). Both TESS and JWST
should launch in 2018.
PLATO instruments
PLATO has 24 normal cameras on board, arranged in four
groups of six. Each of these groups has the same field of view, ESA said, but
they are offset by a 9.2-degree-angle from the vertical axis of the spacecraft.
Additionally, the spacecraft will have two "fast" cameras that will
be used for brighter stars.
If an exoplanet passes in front of a star from the telescope's
perspective, it can cause the light from the star to diminish, affecting its
light curve. Other things can appear like planets, however, such as sunspots on
the star that are darker than the surrounding surface and which also block the
light.
To verify any planets, PLATO will rely on backup
observations from ground-based observatories. These observatories can measure
the radial velocity of the star, or the velocity of the star along the line of
sight from the observer. If slight tugs or movements are seen in the star, this
would imply the presence of a planet due to the effect of the planet's gravity
on the star.
"The key scientific requirement [is] to
detect and characterize a large number of terrestrial planets around bright
stars," ESA wrote in a statement. Terrestrial planets, being small, are
tough to see around stars because they don't dim the star's light as much. The
hope is that by observing closer and brighter stars, the planets will be a
little larger and easier to spot.
The daytime sky on Earth
appears blue in colour. Light is made up of PHOTONS which are matterless
particles. White light is made up of seven colours: red, orange, yellow, green, blue, violet & indigo.
