Solar Sentinels
Encyclopedia
The Solar Sentinels is a space mission to study the Sun
during its solar maximum
, the last before the beginning of the Orion program
. Six spacecraft will be launched, which will separate into three groups. The Solar Sentinels are part of the NASA
program Living With a Star
.
This mission's driving energy is that the solar maximum
of solar cycle 24
will be the final one before the first upcoming manned missions to the Moon
and Mars
. This means that this will be the last chance to understand the solar storms
and the deadly radiation
of a solar maximum
.
, one spacecraft which will take its post near Earth
, and the final sentinel to trail slowly behind Earth
. They are discussed in greater detail below.
at distances of 0.25 AU
. This will be a challenge to scientists and engineers working on these probes, as this is one-fourth the distance between the Earth
and the Sun
. These probes will make in-situ measurements of energetic particles
and plasma
. Instruments to measure X-ray
, radio
, and neutron
emissions will be included. Part of the mission plan includes Venus
flybys.
in UV
and visible light.
magnetic field
. As three spacecraft are needed to completely monitor this magnetic field, partnerships with two other spacecraft will be made: NASA
's Solar Dynamics Observatory
and the European Space Agency
's Solar Orbiter
.
, Japan's Hinode
, the Solar Dynamics Observatory
, and ESA's Solar Orbiter
. Ground-based telescopes will also assist the mission. It will be part of a group of four missions, including the Solar Dynamics Observatory
and the Geospace missions (Radiation Belt Storm Probes
and Ionosphere-Thermosphere Storm Probes
), from the Living With a Star
program.
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
during its solar maximum
Solar maximum
Solar maximum or solar max is the period of greatest solar activity in the solar cycle of the sun. During solar maximum, sunspots appear....
, the last before the beginning of the Orion program
Orion (spacecraft)
Orion is a spacecraft designed by Lockheed Martin for NASA, the space agency of the United States. Orion development began in 2005 as part of the Constellation program, where Orion would fulfill the function of a Crew Exploration Vehicle....
. Six spacecraft will be launched, which will separate into three groups. The Solar Sentinels are part of the NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
program Living With a Star
Living With a Star
Living With a Star is a NASA scientific program to study those aspects of the connected Sun-Earth system that directly affect life and society. LWS is a crosscutting initiative with goals and objectives relevant to NASA's Exploration Initiative, as well as to NASA's Strategic Enterprises...
.
Goals
The goals of the Solar Sentinels are:- Understand the acceleration and transit of solar energetic particlesSolar Energetic ParticlesSolar Energetic Particles are high-energy particles coming from the Sun which had been first observed in the early 1940s. They consist of protons, electrons and heavy ions with energy ranging from a few tens of keV to GeV...
- Understand the initiation and evolution of coronal mass ejections (CMEs) and interplanetary shocks in the inner heliosphereHeliosphereThe heliosphere is a bubble in space "blown" into the interstellar medium by the solar wind. Although electrically neutral atoms from interstellar volume can penetrate this bubble, virtually all of the material in the heliosphere emanates from the Sun itself...
This mission's driving energy is that the solar maximum
Solar maximum
Solar maximum or solar max is the period of greatest solar activity in the solar cycle of the sun. During solar maximum, sunspots appear....
of solar cycle 24
Solar Cycle 24
Solar Cycle 24 is the 24th solar cycle since 1755, when recording of solar sunspot activity began. It is the current solar cycle, and began on . The cycle continues to fall below predictions and is currently exhibiting 50% lower sunspot activity than predicted in May 2009.-Predictions:It is...
will be the final one before the first upcoming manned missions to the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
and Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
. This means that this will be the last chance to understand the solar storms
Solar flare
A solar flare is a sudden brightening observed over the Sun surface or the solar limb, which is interpreted as a large energy release of up to 6 × 1025 joules of energy . The flare ejects clouds of electrons, ions, and atoms through the corona into space. These clouds typically reach Earth a day...
and the deadly radiation
Radiation
In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...
of a solar maximum
Solar maximum
Solar maximum or solar max is the period of greatest solar activity in the solar cycle of the sun. During solar maximum, sunspots appear....
.
Spacecraft
There will be six spacecraft: four identical spacecraft which will explore the inner heliosphereHeliosphere
The heliosphere is a bubble in space "blown" into the interstellar medium by the solar wind. Although electrically neutral atoms from interstellar volume can penetrate this bubble, virtually all of the material in the heliosphere emanates from the Sun itself...
, one spacecraft which will take its post near Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
, and the final sentinel to trail slowly behind Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
. They are discussed in greater detail below.
Inner Heliospheric Sentinels
The majority of the sentinels are the Inner Heliospheric Sentinels (IHS), which will observe the SunSun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
at distances of 0.25 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
. This will be a challenge to scientists and engineers working on these probes, as this is one-fourth the distance between the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
and the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
. These probes will make in-situ measurements of energetic particles
Solar Energetic Particles
Solar Energetic Particles are high-energy particles coming from the Sun which had been first observed in the early 1940s. They consist of protons, electrons and heavy ions with energy ranging from a few tens of keV to GeV...
and plasma
Plasma (physics)
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
. Instruments to measure X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
, radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
, and neutron
Neutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
emissions will be included. Part of the mission plan includes Venus
Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...
flybys.
Near Earth Sentinel
The Near Earth Sentinel (NES) will study the coronaCorona
A corona is a type of plasma "atmosphere" of the Sun or other celestial body, extending millions of kilometers into space, most easily seen during a total solar eclipse, but also observable in a coronagraph...
in UV
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
and visible light.
Farside Sentinel
The Farside Sentinel (FSS) will study the photosphericPhotosphere
The photosphere of an astronomical object is the region from which externally received light originates. The term itself is derived from Ancient Greek roots, φῶς, φωτός/phos, photos meaning "light" and σφαῖρα/sphaira meaning "sphere", in reference to the fact that it is a spheric surface perceived...
magnetic field
Stellar magnetic field
A stellar magnetic field is a magnetic field generated by the motion of conductive plasma inside a star. This motion is created through convection, which is a form of energy transport involving the physical movement of material. A localized magnetic field exerts a force on the plasma, effectively...
. As three spacecraft are needed to completely monitor this magnetic field, partnerships with two other spacecraft will be made: NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
's Solar Dynamics Observatory
Solar Dynamics Observatory
The Solar Dynamics Observatory is a NASA mission which will observe the Sun for over five years. Launched on February 11, 2010, the observatory is part of the Living With a Star program...
and the European Space Agency
European Space Agency
The European Space Agency , established in 1975, is an intergovernmental organisation dedicated to the exploration of space, currently with 18 member states...
's Solar Orbiter
Solar Orbiter
Solar Orbiter is a planned Sun-observing satellite, under development by the European Space Agency . The main mission scenario is a launch by an Atlas V from the Kennedy Space Center in Florida in January 2017...
.
Launch
It is likely the three Inner Heliospheric Sentinels will be launched together. The proposed launch dates are 2012, 2014, 2015, or 2017. The nominal mission lasts three years, with an extension to five years if possible.Cooperation
Several other solar spacecraft will help with this mission, such as STEREOSTEREO
STEREO is a solar observation mission. Two nearly identical spacecraft were launched into orbits that cause them to respectively pull farther ahead of and fall gradually behind the Earth...
, Japan's Hinode
Hinode
Hinode , formerly Solar-B, is a Japan Aerospace Exploration Agency Solar mission with United States and United Kingdom collaboration. It is the follow-up to the Yohkoh mission and it was launched on the final flight of the M-V-7 rocket from Uchinoura Space Center, Japan on 22 September 2006 at...
, the Solar Dynamics Observatory
Solar Dynamics Observatory
The Solar Dynamics Observatory is a NASA mission which will observe the Sun for over five years. Launched on February 11, 2010, the observatory is part of the Living With a Star program...
, and ESA's Solar Orbiter
Solar Orbiter
Solar Orbiter is a planned Sun-observing satellite, under development by the European Space Agency . The main mission scenario is a launch by an Atlas V from the Kennedy Space Center in Florida in January 2017...
. Ground-based telescopes will also assist the mission. It will be part of a group of four missions, including the Solar Dynamics Observatory
Solar Dynamics Observatory
The Solar Dynamics Observatory is a NASA mission which will observe the Sun for over five years. Launched on February 11, 2010, the observatory is part of the Living With a Star program...
and the Geospace missions (Radiation Belt Storm Probes
Radiation Belt Storm Probes
The Radiation Belt Storm Probes is a NASA mission under the Living With a Star program. The goal of the LWS program is to develop the scientific understanding necessary to effectively address those aspects of the connected Sun-Earth system that directly affect life and society...
and Ionosphere-Thermosphere Storm Probes
Ionosphere-Thermosphere Storm Probes
The Ionosphere-Thermosphere Storm Probes is a NASA mission which will study the ionosphere and the thermosphere. This mission is part of the Living With a Star program, the second mission in a pair of geospace missions...
), from the Living With a Star
Living With a Star
Living With a Star is a NASA scientific program to study those aspects of the connected Sun-Earth system that directly affect life and society. LWS is a crosscutting initiative with goals and objectives relevant to NASA's Exploration Initiative, as well as to NASA's Strategic Enterprises...
program.