K-2, K-3, K-4: rocket observatories

In the 60s-70s in Armenia, under the leadership of prof. G. Gurzadyan created the K-2, K-3 and K-4 rocket observatories, which were launched on high-altitude VERTICAL (R-5V) rockets, reaching an altitude of 500 km. The K-2 observatories were intended to study the Sun in the ultraviolet region of the spectrum 3000 – 912 Å and in the soft X-ray region (1-100 Å), and K-3 and K-4 – for studying stars, galaxies and nebulae in the UV range of 3000 – 500 Å. Scientific instruments were placed on a biaxial stabilized platform, in a head capsule separated from the rocket.

R-5B ballistic missiles were launched from the Kapustin Yar cosmodrome. After separation from the rocket at the end of the active phase, the astrophysical probe was stabilized along three axes using a gas propulsion control system with an accuracy of about 1°, and the platform ensured pointing of instruments to the Sun with an error of no worse than 10 arc seconds for a time of approximately 570 seconds. After completing the flight program, the probe with scientific equipment and experimental materials descended to Earth using a parachute system.

The K-2 … K-4 observatories were launched repeatedly in the period from the 60s to the mid-70s, about 10 launches were carried out (RSC Energia). The ROS-5 observatory under the INTERKOSMOS program (PC Polet) was launched 3 times in the late 70s, using more powerful R-14U rockets.

On observatory platforms consisting of a biaxial gimbal, except for the kit of numerous scientific instruments, solar or stellar orientation sensors were also installed, which made it possible, in interaction with the observatory’s tracking system, to stabilize scientific instruments with an accuracy of the order of 20 … 30 arc. sec. for first starts and up to 6…10 arc. sec for the latter.

The mass of the observatory with installed scientific equipment was about 200 kg with overall dimensions dimensions 900×900×900 mm. The work schedule of the K-2 observatory was as follows:

• At an altitude of about 100 km, the rocket fairing was dropped.
• At an altitude of 120 km, the container lid was opened, the observatory platform stabilization sensors captured the Sun and stabilized the platform on it, after which the program began observations.
• On the descending branch of the trajectory (at an altitude of approximately 140 km), the observation program
  ended and the container lid closed.
• After some time, the container was separated from the last stage of the rocket and with the help of a parachute system fell to the surface of the Earth.

• The duration of the program operation of the observatory during the passive phase of the rocket flight is about 570 sec.
• Platform rotation angles along two axes ±30 degrees.
• Solar stabilization accuracy is no worse than ±30 arc. sec.
• Rough solar sensor field of view ±30 degrees
• Accurate solar sensor

        – field of view ±20 arc. minutes
        – resolution 5 arc. sec.
        – lens focal length 2100 mm
        – linear zone 3.2 arc. min.

   

Instrumentation and purpose of scientific equipment of one of the configuration options for the K-2 observatory:

• Lyman-alpha camera – to obtain images of the solar chromosphere in the Lyman-alpha line hydrogen. The focal length of the camera is 500 mm, the lens entrance aperture is 70 mm.
• Coronal slit spectrograph of the Rowland system – for obtaining spectrograms of the corona and solar chromosphere in the range 500-1300 Å with a spectral resolution of 0.1 Å.
• Chromospheric slit spectrograph of the Rowland system – for obtaining spectrograms of the solar chromosphere
  in the range of 700-1800 Å with a spectral resolution of 0.1 Å.
• Out-of-eclipse coronagraph – for obtaining direct images of the solar corona in the wavelength region 2000-3000 Å and to a distance to the solar disk of about 24 solar radii. Inlet diameter holes 16 mm, equivalent focal length – 122 mm.
• Helium monochromator – for obtaining monochromatic images of the Sun in the 304 HeII and 584 HeI. Entrance hole diameter – 50 mm, focal length – 250 mm.
• Pinhole cameras (120 pieces) – for obtaining direct images of the Sun in the soft X-ray region (shorter than 60 Å). The focal length of the cameras is 150 mm, the angular resolution is up to one minute of arc.
• Grazing incidence X-ray spectrograph – to obtain a spectrogram of the solar corona in wavelength range 10 – 150 Å, spectrograph dispersion is about 3 Å/mm.

The results of all devices were recorded photographically, while in most devices, in order to eliminate frictional damage to the emulsion layer, the method of transverse movement of flat cassettes was used, which made it possible to record the results of all exposures of a given launch on a small area of ​​photographic film.

• First detection at an altitude of approximately 400 km of a powerful solar X-ray flare with a flux of 1010 photons/cm2 sec in the 8-60 A band, during the launch on October 1, 1965 (Gurzadyan, 1965);
• X-ray emission was detected that was not associated with sunspots, namely, from an extremely strong prominence, accidentally occurred during observation (flight of October 3, 1970).

After the first successful launches of rocket observatories, options began to be explored for placing these observatories on automatic Earth satellites with the transmission of scientific information to Earth via radio telemetry channels.

K-6 – solar orbital observatory
Hardware composition:

• Short-wave spectrometer BC (300-700 Å).
• Long-wave spectrometer DS (700-1800 Å)
• PC spectrometer (10-130 Å)
• X-ray spectrometer RA (1-3 Å)
• X-ray spectrometer RB (3-10 Å)
• X-ray photometer RF (1-60 Å)

The total weight of the complex is about 150 kg, overall dimensions – diameter 1000 mm.

K-7 – stellar orbital observatory Main task:

• Spectrometry of stars in the range 912-3500 Å up to the seventh magnitude and with a spectral resolution of about 5 Å.
• Photometry of stars up to the ninth magnitude in the region 912-4000 Å using five light filters.

Mainly on K-7 is a mirror telescope with a main mirror diameter of 300 mm. The two tasks posed above are solved by creating two modifications of the K-7 – K-7A and K-7B.

K-7A was designed to solve the first of these tasks – spectrometry of stars. The problem was solved using two spectrometers operating in the ranges 912-1500 Å and 1400-3500 Å. The spectrum was scanned by the daily rotation of the UOS-3 satellite. There was no software search and star guiding.

K-7B was intended for photometry of stars through broadband light filters. A special scanning system located in the focal part of the telescope carried out sequential measurements of the light flux passing through a given filter from a given star. Each range had its own separate radiation receiver (PMT).

K-7 in both versions was to be installed on universal orbital stations (UOS-3 or UOS-M). The expected weight of one set of K-7 is about 150 kg, the overall dimensions are about 1000 mm in diameter.