| Names | Explorer PUNCH SMEX |
|---|---|
| Mission type | Heliophysics |
| Operator | NASA |
| Website | punch |
| Spacecraft properties | |
| Spacecraft type | Orbiters × 4 |
| Bus | Custom, CYGNSS heritage |
| Manufacturer | Southwest Research Institute (SwRI) |
| Launch mass | 40 kg (88 lb) each 160 kg (350 lb) total |
| Start of mission | |
| Launch date | 27 February 2025 (planned) [1] |
| Rocket | Falcon 9 Block 5 |
| Launch site | Vandenberg, SLC-4E |
| Contractor | SpaceX |
| Orbital parameters | |
| Reference system | Geocentric orbit |
| Regime | Sun-synchronous orbit |
| Altitude | 570 km (350 mi) [2] |
| Instruments | |
| Narrow Field Imager (NFI) – 1 satellite Wide Field Imagers (WFIs) – 3 satellites | |
Explorer program | |
Polarimeter to Unify the Corona and Heliosphere (PUNCH) is a future mission by NASA to study the unexplored region from the middle of the solar corona out to 1 AU from the Sun. PUNCH will consist of a constellation of four microsatellites that through continuous 3D deep-field imaging, will observe the corona and heliosphere as elements of a single, connected system. The four microsatellites were initially scheduled to be launched in October 2023, but were moved to launch alongside (rideshare) the SPHEREx space observatory on a Falcon 9 Block 5 rocket from Vandenberg Space Force Base on scheduled to liftoff on 27 February 2025. [3] [1]
On 20 June 2019, NASA announced that PUNCH and TRACERS were the winning candidates to become the next missions in the agency's Small Explorer program (SMEX). [4]
PUNCH is led by Craig DeForest at the Southwest Research Institute (SwRI) in Boulder, Colorado. Including launch costs, PUNCH is being funded for no more than US$165 million. [4]
The stated primary objective of PUNCH is "to fully discern the cross-scale physical processes, from microscale turbulence to the evolution of global-scale structures, that unify the solar corona and heliosphere". [5] In other words, the mission aims to understand how the solar corona becomes the solar wind. [6]
The two specific objectives are to understand how coronal structures become the ambient solar wind, and to understand the dynamic evolution of transient structures in the young solar wind. [5] The Principal Investigator, Craig DeForest, thinks that such closer study will also lead to a better understanding of the causes of solar weather events like coronal mass ejections (CMEs), which can damage satellites and disrupt electrical grids and power systems on Earth. [2] [4]
The more we understand what drives space weather and its interaction with the Earth and lunar systems, the more we can mitigate its effects – including safeguarding astronauts and technology crucial to NASA's Artemis program to the Moon. [4]
The mission configuration consists of a constellation of four observatories, each carrying one primary instrument. [7]
The fields of view (FoV) of the 3 WFIs overlap slightly with each other and with the NFI, and the instruments' operation is synchronized. The instruments operate through polarized Thomson-scatter imaging of the transition from corona to heliosphere. [8] PUNCH integrates images from its constellation of small satellites into a global composite after each orbit, covering ~6 orders of magnitude dynamic range. Through a stream of these images, PUNCH achieves 3D feature localization and accurate deep field imaging. [9] The mission builds on Cyclone Global Navigation Satellite System (CYGNSS) experience with smallsat constellations. [10]
To accomplish its science objectives, PUNCH will acquire polarized white-light images over a composite 90° field of view centered on the Sun, i.e. from a few solar radii to 45° from the Sun in all directions. This poses many challenges in data reduction, meaning that the greatest technical challenge of the mission is in ground-processing the images acquired by the four spacecraft.
The PUNCH science objectives require measuring the faint sunlight reflected off electrons contained in the corona and solar wind (the extended K-corona). Ten degrees from the Sun, the K-corona is 1000x fainter than the background stars, [11] requiring precise photometric calibration across the individual cameras, to measure and remove the background starfield, galaxy, and related features—which constitute 99.9% of the light incident on the cameras. The camera images are co-aligned to within 0.03 pixel RMS, requiring precise measurement of the optical distortion of each lens system. Point spread function effects, such as optical coma, are identified and removed in the PUNCH data reduction pipeline; [12] and minor photometric errors introduced by data compression are also tracked and eliminated. [13] Polarimetry of the K-corona is affected by the polarization of the starfield itself, [14] which required developing a novel formalism to enable background subtraction while preserving linear polarimetry. [15]
The primary PUNCH data product is background-subtracted, polarimetric images produced by the constellation on a 4 minute cadence; these images are made available to everyone via NASA's SDAC facility and the Virtual Solar Observatory.
SwRI is collaborating with the Naval Research Laboratory (NRL) and the Rutherford Appleton Laboratory in Oxfordshire, England, United Kingdom.
PUNCH, which will operate in low Earth orbit, will work in synergy with NASA's Parker Solar Probe and the ESA's Solar Orbiter. [2] [8]
A corona is the outermost layer of a star's atmosphere. It is a hot but relatively dim region of plasma populated by intermittent coronal structures known as solar prominences or filaments.
The solar wind is a stream of charged particles released from the Sun's outermost atmospheric layer, the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between 0.5 and 10 keV. The composition of the solar wind plasma also includes a mixture of particle species found in the solar plasma: trace amounts of heavy ions and atomic nuclei of elements such as carbon, nitrogen, oxygen, neon, magnesium, silicon, sulfur, and iron. There are also rarer traces of some other nuclei and isotopes such as phosphorus, titanium, chromium, and nickel's isotopes 58Ni, 60Ni, and 62Ni. Superimposed with the solar-wind plasma is the interplanetary magnetic field. The solar wind varies in density, temperature and speed over time and over solar latitude and longitude. Its particles can escape the Sun's gravity because of their high energy resulting from the high temperature of the corona, which in turn is a result of the coronal magnetic field. The boundary separating the corona from the solar wind is called the Alfvén surface.
A coronal mass ejection (CME) is a significant ejection of plasma mass from the Sun's corona into the heliosphere. CMEs are often associated with solar flares and other forms of solar activity, but a broadly accepted theoretical understanding of these relationships has not been established.
The Solar and Heliospheric Observatory (SOHO) is a European Space Agency (ESA) spacecraft built by a European industrial consortium led by Matra Marconi Space that was launched on a Lockheed Martin Atlas IIAS launch vehicle on 2 December 1995, to study the Sun. It has also discovered more than 5,000 comets. It began normal operations in May 1996. It is a joint project between the European Space Agency (ESA) and NASA. SOHO was part of the International Solar Terrestrial Physics Program (ISTP). Originally planned as a two-year mission, SOHO continues to operate after 29 years in space; the mission has been extended until the end of 2025, subject to review and confirmation by ESA's Science Programme Committee.
A coronagraph is a telescopic attachment designed to block out the direct light from a star or other bright object so that nearby objects – which otherwise would be hidden in the object's bright glare – can be resolved. Most coronagraphs are intended to view the corona of the Sun, but a new class of conceptually similar instruments are being used to find extrasolar planets and circumstellar disks around nearby stars as well as host galaxies in quasars and other similar objects with active galactic nuclei (AGN).
The heliosphere is the magnetosphere, astrosphere, and outermost atmospheric layer of the Sun. It takes the shape of a vast, tailed bubble-like region of space. In plasma physics terms, it is the cavity formed by the Sun in the surrounding interstellar medium. The "bubble" of the heliosphere is continuously "inflated" by plasma originating from the Sun, known as the solar wind. Outside the heliosphere, this solar plasma gives way to the interstellar plasma permeating the Milky Way. As part of the interplanetary magnetic field, the heliosphere shields the Solar System from significant amounts of cosmic ionizing radiation; uncharged gamma rays are, however, not affected. Its name was likely coined by Alexander J. Dessler, who is credited with the first use of the word in the scientific literature in 1967. The scientific study of the heliosphere is heliophysics, which includes space weather and space climate.
The Solar Maximum Mission satellite was designed to investigate Solar phenomena, particularly solar flares. It was launched on February 14, 1980. The SMM was the first satellite based on the Multimission Modular Spacecraft bus manufactured by Fairchild Industries, a platform which was later used for Landsat 4 and Landsat 5 as well as the Upper Atmosphere Research Satellite.
The Solar Orbiter (SolO) is a Sun-observing probe developed by the European Space Agency (ESA) with a National Aeronautics and Space Administration (NASA) contribution. Solar Orbiter, designed to obtain detailed measurements of the inner heliosphere and the nascent solar wind, will also perform close observations of the polar regions of the Sun which is difficult to do from Earth. These observations are important in investigating how the Sun creates and controls its heliosphere.
Solar physics is the branch of astrophysics that specializes in the study of the Sun. It intersects with many disciplines of pure physics and astrophysics.
Interstellar Boundary Explorer is a NASA satellite in Earth orbit that uses energetic neutral atoms (ENAs) to image the interaction region between the Solar System and interstellar space. The mission is part of NASA's Small Explorer program and was launched with a Pegasus-XL launch vehicle on 19 October 2008.
The Solar Sentinels was a series of proposed space missions to the Sun. Solar Sentinels was proposed in 2006 in conjunction with other Sun missions, and another simpler proposal was submitted in 2008.
The Parker Solar Probe is a NASA space probe launched in 2018 to make observations of the Sun's outer corona.
Energetic Neutral Atom (ENA) imaging is a technology used to create global images of otherwise invisible phenomena in the magnetospheres of planets and throughout the heliosphere.
The Heliophysics Science Division of the Goddard Space Flight Center (NASA) conducts research on the Sun, its extended Solar System environment, and interactions of Earth, other planets, small bodies, and interstellar gas with the heliosphere. Division research also encompasses geospace—Earth's uppermost atmosphere, the ionosphere, and the magnetosphere—and the changing environmental conditions throughout the coupled heliosphere.
Vigil, formerly known as Lagrange, is a space weather mission developed by the European Space Agency. The mission will provide the ESA Space Weather Office with instruments able to monitor the Sun, its solar corona and interplanetary medium between the Sun and Earth, to provide early warnings of increased solar activity, to identify and mitigate potential threats to society and ground, airborne and space based infrastructure as well as to allow 4 to 5 days space weather forecasts. To this purpose the Vigil mission will place for the first time a spacecraft at Sun-Earth Lagrange point 5 (L5) from where it would get a 'side' view of the Sun, observing regions of solar activity on the solar surface before they turn and face Earth.
The Wide-Field Imager for Solar Probe (WISPR) is an imaging instrument of the Parker Solar Probe mission to the Sun, launched in August 2018. Imaging targets include visible light images of the corona, solar wind, shocks, solar ejecta, etc. Development of WISPR was led by the U.S. Naval Research Laboratory. The Parker Solar Probe with WISPR on board was launched by a Delta IV Heavy on 12 August 2018 from Cape Canaveral, Florida. WISPR is intended take advantage of the spacecraft's proximity to the Sun by taking coronagraph-style images of the solar corona and features like coronal streamers, plumes, and mass ejections. One of the goals is to better understand the structure of the solar corona near the Sun.
Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites (TRACERS) is a planned orbiter mission tasked to study the origins of the solar wind and how it affects Earth. TRACERS was proposed by Craig A. Kletzing at the University of Iowa who served as Principal Investigator until his death in 2023. David M. Miles at the University of Iowa was named as Principal Investigator in his stead. The TRACERS mission received US$115 million in funding from NASA.
Space Weather Follow On-Lagrange 1 (SWFO-L1) is a future spacecraft mission planned to monitor signs of solar storms, which may pose harm to Earth's telecommunication network. The spacecraft will be operated by the National Oceanic and Atmospheric Administration (NOAA), with launch scheduled for no earlier than September 2025. It is planned to be placed at the Sun–Earth L1 Lagrange point, a location between the Earth and the Sun. This will allow SWFO-L1 to continuously watch the solar wind and energetic particles heading for Earth. SWFO-L1 is an ESPA Class Spacecraft, sized for launch on an Evolved Expendable Launch Vehicle Secondary Payload Adapter (ESPA) Grande ring in addition to the rocket's primary payload. The spacecraft's Solar Wind Instrument Suite (SWIS) which includes three instruments will monitor solar wind, and the Compact Coronagraph (CCOR) will monitor the Sun's surroundings to image coronal mass ejection (CME). A CME is a large outburst of plasma sent from the Sun towards interplanetary space.
Daniel B. Seaton is an American solar physicist based at the Southwest Research Institute (SwRI) in Boulder, Colorado. He is particularly known for his work on producing and interpreting images of the solar corona, using both visible light and extreme ultraviolet.
Amir Caspi is a solar physicist based at the Southwest Research Institute in Boulder, Colorado. He is particularly known for his work on X-ray spectroscopy of the Sun and the solar corona, and for advancing the art of eclipse observations of the corona to improve scientific understanding.
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