PicSat
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PicSat was a French observatory
nanosatellite A small satellite, miniaturized satellite, or smallsat is a satellite of low mass and size, usually under . While all such satellites can be referred to as "small", different classifications are used to categorize them based on mass. Satellites c ...
, designed to measure the
transit Transit may refer to: Arts and entertainment Film * ''Transit'' (1980 film), a 1980 Israeli film * ''Transit'' (1986 film), a Canadian short film * ''Transit'' (2005 film), a film produced by MTV and Staying-Alive about four people in countrie ...
of
Beta Pictoris b Beta Pictoris b (abbreviated as β Pic b) is an exoplanet orbiting the young debris disk A-type main sequence star Beta Pictoris located approximately 63 light-years (19.4 parsecs, or km) away from Earth in the constellation of Pictor. It has a ...
, an
exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first det ...
which orbits the star
Beta Pictoris Beta Pictoris (abbreviated β Pictoris or β Pic) is the second brightest star in the constellation Pictor. It is located from the Solar System, and is 1.75 times as massive and 8.7 times as luminous as the Sun. The Beta Pictoris s ...
. PicSat was designed and built by a team of scientists led by Dr. Sylvestre Lacour, astrophysicist and instrumentalist at the High Angular Resolution in Astrophysics group in the LESIA laboratory with
Paris Observatory The Paris Observatory (, ), a research institution of the Paris Sciences et Lettres University, is the foremost astronomical observatory of France, and one of the largest astronomical centres in the world. Its historic building is on the Left Ban ...
,
Paris Sciences et Lettres University PSL University (PSL or in French Université PSL, for Paris Sciences et Lettres) is a ''Grands établissements, Grand établissement'' based in Paris, France. It was established in 2010 and formally created as a university in 2019. It is a colle ...
and the
French National Centre for Scientific Research The French National Centre for Scientific Research (, , CNRS) is the French state research organisation and is the largest fundamental science agency in Europe. In 2016, it employed 31,637 staff, including 11,137 tenured researchers, 13,415 engi ...
(CNRS). It was launched on 12 January 2018, and operated for more than 10 weeks before falling silent on 20 March 2018. The cubesat decayed from orbit on 3 October 2023.


Background


Beta Pictoris system

With an age of about 23 million years,
Beta Pictoris Beta Pictoris (abbreviated β Pictoris or β Pic) is the second brightest star in the constellation Pictor. It is located from the Solar System, and is 1.75 times as massive and 8.7 times as luminous as the Sun. The Beta Pictoris s ...
is a very young star. Compared to the Sun, which is 4.5 billion years old, Beta Pictoris is about twice as large in mass and size. Beta Pictoris is relatively close to the Sun: just 63.4 light-years away, making it bright and easy to observe. This makes Beta Pictoris interesting for study as it allows astronomers to learn more about the very early stages of planet formation. In the early 1980s, a large disk of asteroids, dust, gas, and other debris were found surrounding Beta Pictoris, leftovers from the formation of the star. In 2009, a giant
gas planet A gas giant is a giant planet composed mainly of hydrogen and helium. Jupiter and Saturn are the gas giants of the Solar System. The term "gas giant" was originally synonymous with "giant planet". However, in the 1990s, it became known that Uranu ...
orbiting Beta Pictoris was discovered by a team of French astronomers led by Anne-Marie Lagrange from
Grenoble, France Grenoble ( ; ; or ; or ) is the prefecture and largest city of the Isère department in the Auvergne-Rhône-Alpes region of southeastern France. It was the capital of the Dauphiné historical province and lies where the river Drac flows in ...
. The planet, named
Beta Pictoris b Beta Pictoris b (abbreviated as β Pic b) is an exoplanet orbiting the young debris disk A-type main sequence star Beta Pictoris located approximately 63 light-years (19.4 parsecs, or km) away from Earth in the constellation of Pictor. It has a ...
, is about seven times as massive as
Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...
. It orbits Beta Pictoris from a distance at around ten
astronomical unit The astronomical unit (symbol: au or AU) is a unit of length defined to be exactly equal to . Historically, the astronomical unit was conceived as the average Earth-Sun distance (the average of Earth's aphelion and perihelion), before its m ...
s: ten times the distance between the Earth and the Sun, and about the same distance between Saturn and the Sun. In 2016, it was predicted that Beta Pictoris b's
Hill sphere The Hill sphere is a common model for the calculation of a Sphere of influence (astrodynamics), gravitational sphere of influence. It is the most commonly used model to calculate the spatial extent of gravitational influence of an astronomical ...
or the planet itself would be passing in front of its star as seen from the Earth. The detailed observation of such a transit would reveal detailed information about the planet, such as its exact size, the composition of its
atmosphere An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...
, its density, and its chemical composition. Because Beta Pictoris b is so young, this information would reveal more about the formation of giant planets and
planetary system A planetary system is a set of gravity, gravitationally bound non-stellar Astronomical object, bodies in or out of orbit around a star or star system. Generally speaking, systems with one or more planets constitute a planetary system, although ...
s. However, as Beta Pictoris b's orbit is not well known, the moment of transit could only be estimated roughly. The transit was predicted to occur between the summer of 2017 and the summer of 2018. A transit of the planet would have lasted only a few hours; a transit of the planet's Hill sphere would have lasted anywhere from days to months. Continuous monitoring would have been the only way to capture the phenomenon. Since Earth-based observatories would not be able to accurately capture the transit, as long-term continuous monitoring was unlikely to work with Earth's atmosphere, day-night cycle changes, and scheduling conflicts, only a satellite could accurately capture the transit. The purpose of PicSat was to continually observe Beta Pictoris' brightness in order to capture the change in brightness when Beta Pictoris b transited over the star and partially blocked some light.


Project

PicSat, a contraction of "Beta Pictoris" and "satellite", was a
CubeSat A CubeSat is a class of small satellite with a form factor of cubes. CubeSats have a mass of no more than per unit,, url=https://static1.squarespace.com/static/5418c831e4b0fa4ecac1bacd/t/5f24997b6deea10cc52bb016/1596234122437/CDS+REV14+2020-07-3 ...
. PicSat was composed of three standard cubic units, called a "3U", each 10x10x10cm in size. PicSat was the first CubeSat to be operated by the CNRS. It was different from most CubeSat projects in that it was developed by professionals, not by students. The project began in 2014 when Sylvestre Lacour, astrophysicist and instrumentalist at the French CNRS at the LESIA laboratory / Paris Observatory, thought of using a CubeSat to observe Beta Pictoris b's transit. He gathered a small team and they designed and built PicSat. PicSat was one of the few CubeSats worldwide with an astrophysical science goal and the first CubeSat in the field of exoplanetary science. The PicSat science case was defined in collaboration with Dr. Alain Lecavelier des Etangs from the Institut d’Astrophysique de Paris, who had been working on the Beta Pictoris system for many years. The PicSat project also involved a collaboration with CCERES, the "Center & Campus" space of PSL Research University, and with French Space Agency
CNES CNES () is the French national space agency. Headquartered in central Paris, the agency is overseen by the ministries of the Armed Forces, Economy and Finance and Higher Education, Research and Innovation. It operates from the Toulouse Spac ...
experts.


Specifications

PicSat consisted of three cubic units. The top and middle cubic units held the satellite's payload, and the bottom unit contained its onboard computer. PicSat's topmost unit contained a small telescope with a five-centimeter diameter mirror. The mirror's small size was sufficient, as Beta Pictoris is very bright. The middle unit contained two innovative technical tools: its fine-tracking ability, and its usage of a thin
optical fiber An optical fiber, or optical fibre, is a flexible glass or plastic fiber that can transmit light from one end to the other. Such fibers find wide usage in fiber-optic communications, where they permit transmission over longer distances and at ...
, 3 micrometers in diameter. The fiber, whose usage marks the first time an optical fiber was flown into space, receives light photons and guides them to a sensitive photodiode that accurately measures the arrival time of each individual photon. Using a thin optical fiber eliminated other light sources, like stray light from the sky and scattered light from within the optical system, from entering the photodiode, allowing for accurate measurement of Beta Pictoris' brightness. A fast-moving piezoelectric actuator was added to PicSat to keep the optical fiber tracked upon Beta Pictoris, since the natural wobble of the satellite's orbit would affect the fiber's ability to accurately track and measure the star. The bottom cubic unit of PicSat contained the onboard computer for the satellite's operation, ground-station communication with Earth, raw pointing of the telescope, battery operation, and other important monitoring tasks. The whole satellite was clothed in arrays of deployable solar panels, providing energy for all systems. PicSat's total weight was about 3.5 kilograms, and its power consumption was about 5 watts.


Telescope support

If PicSat ever detected the onset of Beta Pictoris b's transit, or the transit of its Hill sphere, then a
European Southern Observatory The European Organisation for Astronomical Research in the Southern Hemisphere, commonly referred to as the European Southern Observatory (ESO), is an intergovernmental organization, intergovernmental research organisation made up of 16 m ...
telescope would have been immediately put into action. This was thanks to an accepted proposal to ESO for an opportunity to observe time in support of the PicSat project, led by Dr. Flavien Kiefer from the
Institut d'astrophysique de Paris The Institut d'Astrophysique de Paris (translated: Paris Institute of Astrophysics) is a research institute in Paris, France. The Institute is part of the Sorbonne University and is associated with the CNRS Centre national de la recherche scientif ...
. Dr. Kiefer was known for his work on the detection and observation of
exocomet An exocomet, or extrasolar comet, is a comet outside the Solar System, which includes rogue comets and comets that orbit stars other than the Sun. The first exocomets were detected in 1987 around Beta Pictoris, a very young A-type main-sequence ...
s in star systems such as Beta Pictoris. The telescope was equipped with the High Accuracy Radial Velocity Planet Searcher (HARPS) instrument. Together with PicSat measurements, HARPS transit data would have allowed for more accurate determinations of the orbit and size of the planet, along with the chemical make up of its atmosphere. If a
comet A comet is an icy, small Solar System body that warms and begins to release gases when passing close to the Sun, a process called outgassing. This produces an extended, gravitationally unbound atmosphere or Coma (cometary), coma surrounding ...
were to have transited, HARPS would have been able to determine the chemical composition of the comet's atmosphere, which carries key information about the chemical composition of the star system as a whole and thus its formation and evolution.


Operation

PicSat was launched into a
polar Polar may refer to: Geography * Geographical pole, either of the two points on Earth where its axis of rotation intersects its surface ** Polar climate, the climate common in polar regions ** Polar regions of Earth, locations within the polar circ ...
,
low Earth orbit A low Earth orbit (LEO) is an geocentric orbit, orbit around Earth with a orbital period, period of 128 minutes or less (making at least 11.25 orbits per day) and an orbital eccentricity, eccentricity less than 0.25. Most of the artificial object ...
with an altitude of 600 km on 12 January 2018. The launch was carried out by the
Indian Space Research Organization The Indian Space Research Organisation (ISRO ) is India's national space agency, headquartered in Bengaluru, Karnataka. It serves as the principal research and development arm of the Department of Space (DoS), overseen by the Prime Minister o ...
using a
Polar Satellite Launch Vehicle The Polar Satellite Launch Vehicle (PSLV) is an expendable medium-lift launch vehicle designed and operated by the Indian Space Research Organisation (ISRO). It was developed to allow India to launch its Indian Remote Sensing (IRS) satellite ...
on the
PSLV-C40 PSLV-C40 was the 42nd mission of the Indian Polar Satellite Launch Vehicle (PSLV) program in the XL configuration. PSLV-C40 successfully carried and deployed 31 satellites in Sun-synchronous orbits. Overview Two Surrey Satellite Technology sate ...
mission. The satellite was operated from the PicSat Ground Station at
Paris Observatory The Paris Observatory (, ), a research institution of the Paris Sciences et Lettres University, is the foremost astronomical observatory of France, and one of the largest astronomical centres in the world. Its historic building is on the Left Ban ...
, although it only was visible for about 30 minutes a day. Since PicSat communicated with amateur radio frequencies (achieved with cooperation with Réseau des Émetteurs Français), anyone with radio receiving capabilities was able to tune into, receive, and upload information from PicSat to a database. A large network of radio amateurs were called to collaborate to track the satellite, receive its data, and transmit it to Ground Station. Licensed radio amateurs were able to use PicSat as a
transponder In telecommunications, a transponder is a device that, upon receiving a signal, emits a different signal in response. The term is a blend of ''transmitter'' and ''responder''. In air navigation or radio frequency identification, a flight trans ...
when it was not performing observation tasks or other communication. PicSat's official website displayed received information, as well as up-to-date
light curve In astronomy, a light curve is a graph (discrete mathematics), graph of the Radiance, light intensity of a celestial object or region as a function of time, typically with the magnitude (astronomy), magnitude of light received on the ''y''-axis ...
data of Beta Pictoris. PicSat was predicted to operate for one year. It operated for approximately 10 weeks before contact was lost on 20 March 2018. Attempts to reestablish contact were made. On 30 March it was believed contact was restored by a team at
Morehead State University Morehead State University (MSU) is a public university in Morehead, Kentucky, United States. The university began as Morehead Normal School, which opened its doors in 1887. The Craft Academy for Excellence in Science and Mathematics, a two-yea ...
, but the signal received was from the TIGRISAT satellite. The mission officially concluded on 5 April.


Supporting institutions

PicSat was financially supported by the
European Research Council The European Research Council (ERC) is a public body for funding of scientific and technological research conducted within the European Union (EU). Established by the European Commission in 2007, the ERC is composed of an independent Scientific ...
(ERC) under the European Union's
Horizon 2020 The Framework Programmes for Research and Technological Development, also called Framework Programmes or abbreviated FP1 to FP9, are funding programmes created by the European Union/European Commission to support and foster research in the Europe ...
research and innovation program Lithium proposal 639248, the CNRS, the ESEP Laboratory Group, the PSL Research University, Foundation MERAC,
CNES CNES () is the French national space agency. Headquartered in central Paris, the agency is overseen by the ministries of the Armed Forces, Economy and Finance and Higher Education, Research and Innovation. It operates from the Toulouse Spac ...
, CCERES, and the Paris Observatory – LESIA.


See also

*
Methods of detecting exoplanets Methods of detecting exoplanets usually rely on indirect strategies – that is, they do not directly Astrophotography, image the planet but deduce its existence from another signal. Any planet is an extremely faint light source compared to its ...
*
Photometry (astronomy) In astronomy, photometry, from Greek '' photo-'' ("light") and '' -metry'' ("measure"), is a technique used in astronomy that is concerned with measuring the flux or intensity of light radiated by astronomical objects. This light is measured t ...


References


External links

* * PicSat Flickr account (photos of the satellite, the team, etc.)
PicSat Beta-Pictoris Star System Info Sheet
{{Portal bar, Astronomy, Spaceflight CubeSats Space telescopes Spacecraft launched in 2018 Paris Observatory Space science experiments Satellites of France 2018 in France Beta Pictoris