The LPI project to explore new frontiers in quantum astronomy from La Palma

The Instituto de Astrofísica de Andalucía (IAA-CSIC) is leading the LPI (La Palma Interferometer) project, aimed at conducting astronomical observations with spatial resolution a thousand times greater than that of the Hubble and James Webb space telescopes.

LPI brings together the collaboration of various research centers and institutions from Spain, Italy, the Nordic countries, and Mexico, working together to establish a cutting-edge scientific facility with international relevance.

 

 

05/12/2024

Interferometry arrived decades ago to revolutionize astronomy, overcoming the limitations of individual telescopes. This technique combines the signals from multiple antennas or telescopes, achieving resolutions and sensitivities unattainable with a single telescope. Until now, this advancement has primarily been applied in radio waves, with facilities like ALMA (Atacama Large Millimeter/submillimeter Array), and in infrared, with the VLTI (Very Large Telescope Interferometer) of the European Southern Observatory, located in northern Chile.

The LPI (La Palma Interferometer) project, led by the IAA-CSIC, proposes a new approach that seeks to combine the light of several optical telescopes at the Roque de los Muchachos Observatory (ORM) using a technique called intensity interferometry. Unlike other forms of interferometry, this methodology allows the study of photon correlations in the visible spectrum, opening new possibilities for astronomical research.

“With state-of-the-art single-photon detection technology developed in Spain and unprecedented time synchronization, the La Palma Interferometer sets a new frontier in astronomy, enabling us to explore the universe like never before with unmatched precision,” explains Francisco Prada, principal investigator of the project and researcher at the IAA-CSIC.

In addition to leading the new interferometer project, the IAA-CSIC is also responsible for the optical design of the SPAD cameras—extremely sensitive light-detection devices—and for the development of data analysis, actively contributing to the project’s scientific goals. “Leading the LPI project positions Spain at the forefront of quantum astronomy, paving the way for a bright future with the development of next-generation technologies,” says Professor Francisco Prada (IAA-CSIC).

 

 

Google Earth image of the Roque de los Muchachos Observatory on La Palma, showing the arrangement of the five optical telescopes of the LPI interferometer. The colored lines indicate the baselines to be implemented in different phases, connecting the GTC, TNG, NOT, WHT and INT telescopes. The telescopes are connected through the optical fiber network of the Instituto de Astrofísica de Canarias and RedIRIS. The distance between GTC and INT is 1.5 km. In the lower right corner, a scale diagram of interferometers such as VLTI and CHARA is shown. Credit: Eisenhauer et al., 2023, ARAA, 62, 237

MISSION AND OBJETIVES

The LPI project will carry out astronomical observations using intensity interferometry and next-generation microchip-SPAD (Single-Photon Avalanche Diode) sensors developed at the  Instituto de Microelectrónica de Sevilla (IMSE CSIC-US). Additionally, the control electronics for these sensors have been designed by the Escuela Politécnica Superior de la Universidad Autónoma de Madrid (EPS-UAM). Thanks to this innovative technology, the project will achieve spatial resolution a thousand times superior to that of the Hubble and James Webb space telescopes, enabling the study of astronomical phenomena under extreme conditions, such as the accretion disks of black holes and ultra-fast transient events. Furthermore, temporal precision in the picosecond range—equivalent to one trillionth of a second—will be achieved, a timeframe so brief that light would travel only 0.3 millimeters in that period.

LPI is negotiating its installation at the Roque de los Muchachos Observatory (ORM), part of the network of Singular Scientific and Technical Infrastructures (ICTS) of the Observatorio de Canarias, managed by the Instituto de Astrofísica de Canarias (IAC).

The deputy director of the IAC, Eva Villaver, is confident that “the technological and instrumental development involved in this project at the ORM will contribute to a better understanding of the Universe from one of the best locations for Astronomy on the planet.” She also highlights the collaboration between the IAA and the IAC, which share scientific goals and values aimed at strengthening the leadership of Spanish Astrophysics on the international stage.

If the project’s installation at ORM is approved, LPI will begin its observations in a first phase using the TNG (Telescopio Nazionale Galileo), equipped with a 3.6-meter primary mirror, and the Nordic Optical Telescope (NOT), with a 2.5-meter mirror. Additionally, contact has already been established with the directors of the Gran Telescopio Canarias (GTC), which has a 10.4-meter mirror, and conversations are expected to begin with the Isaac Newton Group of Telescopes (ING), also located in La Palma, to expand the telescope network in subsequent phases.

 

LPI telescopes

 

 

A TECHNOLOGICAL CHALLENGE

Thanks to advances in ultra-fast readout SPAD sensors and the network of optical telescopes at the Roque de los Muchachos, the LPI project will correlate signals over extremely short timescales. This will enhance observation sensitivity and achieve resolutions of 50 microarcseconds—a very small angular measurement—comparable to those of the Event Horizon Telescope (EHT) but in the visible spectrum. To accomplish this, time synchronization at the picosecond level will be required—a technological challenge that will benefit from the extensive expertise of the Real Instituto y Observatorio de la Armada (ROA), the ORM of the IAC, and RedIRIS, the Spanish academic and research network that provides advanced communication services to the scientific community and national universities.

Currently, the only operational interferometer in the visible spectrum is CHARA, located on Mount Wilson, which combines the light of six 1-meter telescopes with baselines —distance between two telescopes within an interferometry network— of up to 330 meters. In contrast, LPI, with its installation on larger optical telescopes at the Roque de los Muchachos Observatory and a baseline of 1.5 kilometers, will be able to observe much fainter objects, achieving a resolution four times higher. This is equivalent to the angular size of a one-euro coin seen from 65,000 kilometers away, opening new possibilities for observing the universe.

 

Aerial view of the Roque de los Muchachos Observatory (ORM) on La Palma, where the LPI project will be developed. Credits: Daniel López, Instituto de Astrofísica de Canarias (IAC)/ EST Solar Telescope Gallery

 

 

PROJECT LAUNCH MEETING

During the project’s kick-off meeting, held on November 7-8 at the Real Instituto y Observatorio de la Armada (ROA) in San Fernando, Cádiz, presentations were given focusing on various scientific aspects. Key topics included time synchronization, the design of microchip-SPAD sensors and their control electronics, the development of SPAD cameras, and the statistical and artificial intelligence techniques required to analyze photons observed simultaneously with LPI’s telescope network.

Opening remarks were delivered by Antonio Pazos, director of the ROA; Ana Castro, Vice President for Innovation and Knowledge Transfer at CSIC; Antxon Alberdi, director of the IAA-CSIC; and Professor Francisco Prada, principal investigator of LPI at the IAA-CSIC, who highlighted the scientific and technological importance of the project.

Researchers and technologists from various institutions participated in the meeting, including the Real Instituto y Observatorio de la Armada (ROA); the Instituto de Astrofísica de Andalucía (IAA-CSIC); the Instituto de Astrofísica de Canarias (IAC); the Instituto de Microelectrónica de Sevilla (IMSE CSIC-US); the Escuela Politécnica Superior de la Universidad Autónoma de Madrid  (EPS-UAM); the Spanish academic and research network that provides advanced communication services to the scientific community and national universities (RedIRIS), the Galileo Galilei Foundation (INAF, TNG), the Nordic Optical Telescope (NOT), the Gran Telescopio Canarias (GTC), the Department of Fundamental Physics of the University of Salamanca (USAL), the Department of Electronics and Computer Science of the University of Granada (UGR), and the Instituto de Astronomía de la Universidad Nacional Autónoma de México (UNAM).

 

Participants in the LPI Interferometer launching workshop. The image shows the San Fernando Meridian, which passes through the ROA, and was the reference for all Spanish nautical cartography until 1884, when at the Washington Conference the Greenwich Meridian was established as the universal 'Zero Meridian'.

 
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