The "Interheliozond" project is intended for the studies of the solar physics and solar-terrestrial relations. It is planned to launch the "Interheliozond" spacecraft in 2022. Making multiple gravitational evolutions near the Venus this probe will step-by-step move to the Sun and will make numerous measurements. The Leading researcher, DSc. Sergey Svertilov told us about this project.
- Sergey, please, tell us what is the SINP input into the project?
- We develop two instruments: detector "InterSONG" and telescope SKI-5. "InterSONG" is mainly intended for the measurements of neutron flux produced by the Sun. SKI-5 will measure flux of high-energy charged particles also produced by the Sun. First of all they are electrons with energy from 100 keV up to several MeV, protons with energy from several MeV up to 100 Mev and some nuclei with energy from several MeV/nucleon up to several dozens MeV/nucleon.
- What are the purposes of the "InterSONG" and SKI-5 instruments?
- Neutrons detector "InterSONG" first of all will determine the direction of the detected particles coming. It will allow direct showing that the neutrons came from the Sun. Previously using detectors on the Earth's orbit we only supposed that we detected neutrons from the Sun, because we had no direct proof.
On the second hand, the neutrons are unstable particles, therefore the nearer instrument to the Sun the higher the probability that we'll be able to detect neutrons of lower energy. We'll have an opportunity to measure flux of neutrons, which are less available on the Earth's orbit!
On the third hand, neutrons will provide information about acceleration of the protons or nuclei of other elements in the region of solar flare. It is important in order to understand flare's mechanism and to determine composition of the matter in the region of the flare. We'll fin out if there any other elements in the solar atmosphere besides protons and electrons plasma.
Charged particles telescpe SKI-5 is mainly intended for radiation measurements. If during the solar flare the particles are accelerated and leave the solar corona, SKI-5 will allow their registration and measurement of their energy spectra, i.e. energy distribution of particles flux. It will provide information about particles' acceleration during the flares.
Besides, SKI-5 is able to measure angular distribution of fluxes of high-energy charged particles, which can help us to understand on what trajectories do particles move from the Sun, where does acceleration happen and does it happen only during the flare. But in order to answer these questions it is necessary to measure charged particles flux in the different points of interplanetary space. It will be very good, if measurements are carried out simultaneously by the "InterSONG" instrument relatively close to the Sun and by other scientific instruments onboard spacecrafts near the Earth.
- Is it possible to organize simultaneous measurements?
- There are always a lot of spacecrafts on the near-Earth orbits, so probability is quite high.
- What will the obtained knowledge provide?
- Our interests are fundamental. We'll develop an abequare model of particles acceleration. Probably, we'll be able to answer a question: why do natural particles accelerators work?
- What is the current status of the project?
- The stage of mockup-level will continue till 2015. If next year financing is enough, we'll start the stage of development engineering.
Previously we carried out research and development and preliminary development engineering, in particular, we developed project definition. These stages are mainly paper-based.
Soon we'll begin to develop the laboratory models of separate detectors' units, electronics, photodetectors. Then we'll choose one or another design and, correspondingly, one or another detector, photodetector, electronic circuit, etc. by means of the laboratory tests. In such a way the final design of the instrument will be developed.
Up to 2015 we'll manufacture the first model of the instrument which will fully conform to the flight model. The only exception is that instead of detectors and electronics the first model will include a sort of dummy (a lamp, resistor or transistor, which will copy current-consumption and heat generation). The first model will also run the laboratory tests. According to the results of the tests the documents will be finally changed, the final document for the production of the technological and flight models will be published.
- Are there analogous instruments in the world?
- No, there are no such instruments, the equipment which we plan to develop is unique. There are analogous scientific purposes, basing on which analogous instruments are being developed.
- Please, tell us details...
- The "InterSONG" ia unique by the combination of hodoscope system and calorimeter.
Meanwhile we consider the variant of the instrument, which includes a hodoscope system consisting of a set of fibers based on plastic scintillator and located in a criss-cross manner. Each fiber is of several millimeters thick and 30-40 cm long.
The substance is that when a neutron comes into the fiber, it begins to glow. This glow is detected by photodetector, placed on the end face of the fiber. It is important that the signal obtained from the separate fiber allows obtaining of coordinates of the interaction of the neutron and the fiber, and further - trajectory of the neutron.
Under the hodoscope system a calorimeter should be located. It is a cube consisted of numerous finger-shaped crystals. It is also scintillator, which glows after the particles fall on it. It should be manufactured from the more condensed matter in order to detect gamma-emission. Most probably aluminium-yttrium orthosilicates will be used as scintillator's matter, because they are not water-absorbing, does not need specific protection from water.
The SKI-5 instrument consists of 5 telescopes and 3 silicon detectors. Meanwhile its variant is standard for such instrument, but we are going to improve it. Probably, we'll add some additional channels for detection of the particles with lower energy in order to extend the ranges. Probably, we'll add detectors in order to measure angular disctributions more accurately.
- Are there any weight limitations for the instrument?
- Yes, the limitations are very rigid, because, as you understand, the spacecraft needs to fly far away, launch is very expensive and we want to mount many instruments onboard. Due to design improvement we'll keep weight restrictions. Now it is too early to state it, but probably we'll use not only traditional metallic elements, but also more light carbon-fiber elements. But it needs additional development, which will take two years. The weight of the "InterSONG" instrument must be not more than 8 kilograms, of the SKI-5 - up to 5 kilograms. The limitations are not large for the instruments of such class.
- How now can you evaluate instruments' efficiency?
- The efficiency is calculated. It's a complicated calculation be means of many graphs. The efficiency can be evaluated by a number of neutrons, detected during one flare - from several neutrons up to dozens of neutrons.
- What is lifetime of the instruments?
- Our instruments should work not less that the spacecraft. Although my experience shows that scientific equipment lives longer than spacecrafts. In all experiments, where I took part, the spacecrafts became disable ealier than scientific equipment.
- These instruments will be also operated so long?
- I'm sure, yes. For instance, the instruments onboard the satellite "CORONAS-F" were operated 5.5 years instead of warranty lifetime of 3 years. Onboard the American spacecraft "Voyager" the equipment is under operation during almost 40 years. Conceptually, properly developed and manufactured instruments are able for operation during very long periods of time - dozens of years.