A new orbital telescope will be developed basing on KLPVE and JEM-EUSO instruments

Integrability of the KLPVE and JEM-EUSO projects was disscussed during the international meeting which took place at SINP

An International meeting for the discussion of integrability of two scientific projects - Russian project KLPVE and International one JEM-EUSO - took place at SINP MSU.

KLPVE (Russian abbreviation for Ultra High Energy Cosmic Rays) is an orbital reflecting telescope which represents a concentrating mirror of big size and photoelectric detector consisting of photomultipliers. A parent organization of the project is SINP MSU, principal investigators are Mikhail Panasyuk and Boris Khrenov.

JEM-EUSO (Japanese Experiment Module — Extreme Universe Space Observatory) is an orbital wide-angle optical telescope consisting of three Fresnel lenses. Parent organization of the project is RIKEN Physical Institute of Japan, principal investigator is Piergiorgio Picozza (Università degli Studi di Roma Tor Vergata) and National Institute of Nuclear Physics (INFN).

The main goal of both projects is to study ultra-high energy cosmic rays of extragalactic origin. Currently they are at the conceptual design stage.

"These projects - KLPVE and JEM-EUSO - are very complicated from the point of technology and price. In order to get ahead it is necessary to join efforts of several scientific groups, several countries. At the same time both experiments have the same scientific goals and it is more productive to join our efforts and work together. It is also important that many scientists, including me, in particular, have positive experience of collaboration with Russian colleagues: they work fine and we succeeded in realization of several space experiments and would like to continue our collaboration. It is necessary to note, that this experiemnt has already got support of the Russian space agency Roscosmos, and it is very important for the beginning of the joint research", - Professor Piergiorgio Picozza told us.

Japan agency of aerospace research - JAXA (which took the initiative in JEM-EUSO project, when ESA refused from it) also maintains cooperation with Russia. RIKEN representative Toshi Ebisuzaki explained us: "JEM-EUSO is a very expensive project, and our means are too small for it, therefore JAXA had to stop its funding. But there is an existing project KLPVE, and our colleagues from MSU offered to join our forces. Russian party takes the bulk of the work and financing of the project. We'll take part in the development of the separate parts of the equipment in order to improve characteristics and quality of the instruments."

Then he told us about the planned works of the Japan party: "First of all we'll manufacture correcting lenses, because originally the KLPVE instrument is only a mirror telescope, and its field of view is sufficiently small. Using correcting lenses like our glasses it is possible to improve optic system operation significantly, to increase its field of view in the atmosphere. The lense will make the image more sharply defined, i.e. the size of the spot at the focal plane will be smaller. Therefore we'll be able to use smaller pixels of the photoelectric detector. Like in the camera: smaller pixel provides higher quality of the image. We can use phtomultipliers with a small photocathode produced in Japan. And lastly, in order to record cosmic rays it is necessary to know atmospheric structure during the observations. So Japan party plans to take part in the development of lidar - a monitoring system for the atmosphere, more exactly, one of its parts. Lidar is a device which emits laser beam into the atmosphere and measures scattered and reflected signals and delay time. We need to know if there are clouds in the field of view or not, because if there are, like today, it is impossible to detect comsic rays, or at least we need to know at what altitude they are situated."

As a member of the Executive Board of the JEM-EUSO project SINP MSU Director, Professor Mikhail Panasyuk offered to join the projects JEM-EUSO and KLPVE. The KLPVE experiment currently is included into the long-term program of scientific and applied experiments onboard the Internaltional Space Station (ISS) and have passed the stage of preliminary development - so-called conceptual design stage.

"The project KLPVE is sequel of the SINP experiments onboard the satellites "Universitetsky-Tatiana", "Universitetsky-Tatiana-2" and "Lomonosov" which were devoted to the studies of fast phenomena within UV range in the Earth's atmosphere. But detectors onboard "Tatiana" series satellites were designed for the studies of powerful discharges in the high atmosphere, and detectors TUS onboard "Lomonosov" and KLPVE onboard ISS will study ultra-high energy cosmic rays. Currently SINP scientists are working at the simulation and selection of the parameters of optic systems and photoelectric detector, develop detector's electronics and separate mechanical systems. I think that we'll make a good job of it due to our experience in development of the TUS detector for the "Lomonosov" satellite and in participation in JEM-EUSO collaboration. Russian space corporation "Energija" also plays a key role in the project, because it is responsible for the integration of the instrument to the ISS and many parameters and limits depends on it," - SINP senior researcher Pavel Klimov, responsible for the KLPVE project told us.

Professor Piergiorgio Picozza added: "We have a very hegh-defined plan of the project's realization for the nearest time. We have already began to sign some very important joint documents and have confirmed an International working party consisted of the members of both experiments - JEM-EUSO and KLPVE. This party have already started its work, and we hope that in a few months we'll be able to choose one of the offered variants of the joint experiment."

As Pavel Klimov said, there are four variants of the improvement of the existing international instrument based on the KLPVE and JEM-EUSO.

The first of them, basic variant, needs minimum changes in the primary project. It is offered to dispose a correcting lense between the mirror and the photoelectric receiver. Due to it the size of the image will become several times smaller. It in turn will allow to use smaller pixels for detection. Currently in KLPVE instrument the size of the photoelectric detector's cell is 15x15 mm, and in the multi-anode photomultipliers of the JEM-EUSO project - 3x3 mm. Decresing of the cell's size will improve resolution of the instrument and quality of the detected events. Field of view of the new instrument will be ± 14 degrees instead of ± 7 degrees of the KLPVE.

The second variant implies separation of the instrument into three telescopes with smaller mirrors - each of 4 sq.m., and displacement of them in a way to observe different regions of the atmosphere. Then signal in each telescope will be sharp and field of view of the total instrument will be significantly increased. There are some advantages of this design: for instance, rotation of different telescopes will provide variation of fields of view of the telescopes, their expositions and thresholds. But there are also disadvantages: complicated and expensive delivery and installation of a bulky instrument onboard ISS.

Following two variants - development of the JEM-EUSO analogue basing only on lense optics, or development of the analogue of the mirror Schmidt telescope - have the same drawbacks. But such telescopes can provide better scientific results, because their field of view will be up to 20-30 degrees.

"The projects differ in the type of the optic system: mirror for the KLPVE and lenses for the JEM-EUSO. We are going to use small variant of JEM-EUSO lenses in order to correct image in the KLPVE detector. So the mirror will provide high optical efficiency of the instrument, and the lense will provide high quality image. It is also supposed to use photomultipliers and electronics from the JEM-EUSO project for the whole or the parts of photoelectric detector, and atmospheric monitoring system - IR camera and lidar", - Pavel Klimov resumed.

Currently more distant plans such as launching dates are not clear, because a new international project needs long time for development and production. But Pavel hopefully concluded: "It is very important that ISS operation was prolonged till 2024. At the same time the instrument is needed to be operated on orbit not less than during five years in order to collect sufficient data volume. Therefore I think, that we have to get a jerk on the project and to install the instrument onboard ISS as soon as possible, but surely it must be high-quality instrument!"

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