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Spektr-RG mission






Above: The trajectory proposed for the Intergelio-Zond mission would take the spacecraft on a complicated spiral into the vicinity of the Sun with the help of the gravitational fields of the Earth and Venus. (Red lines indicate powered flight of the probe under the thrust of its electric engines. Dotted lines show the orbits of Earth, Venus and Mercury.) Credit: Roskosmos

Previous chapter: Unmanned missions beyond Mars and Venus

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Russia to send spacecraft into vicinity of the Sun

In 2012, the Russian space agency gave the go head to the full-scale development of an ambitious spacecraft dedicated to studies of the Sun from a close distance. The first Russian or Soviet mission into the vicinity of the Sun faces many unprecedented technical challenges including the development of innovative electric engines and protecting the spacecraft from the searing 600-degree heat and radiation of our home star. Dubbed Intergelio-Zond or IGZ, the daring space probe would follow in the footsteps of the US-German Helios mission and NASA's Ulysses spacecraft. It was also developed in parallel with the US Solar Probe and the European Solar Orbiter projects.

Mission to the Sun

Russian space scientists have been considering the Intergelio-Zond project since 1997, however the idea remained in embryonic stage until around 2008. At that time, the Russian space agency, Roskosmos, finally committed to finance the project as an addition to the Federal space program covering the period from 2005 to 2015. The agency gave NPO Lavochkin around a year and a half from January 2009 to May 2010 to develop a Technical Proposal for the mission. According to the plans at the time, the 8,120-kilogram spacecraft would be launched by a Soyuz-2 rocket in 2014, carrying more than 300 kilograms of scientific gear.

Scientists hoped that Intergelio-Zond would approach the Sun to a distance equal to 30 or 40 of its radii. (434), however by 2010, the closest point was moved back to 60-70 solar radii (still slightly closer to the Sun than the orbit of Mercury). According to estimates, the probe would need nearly two years to cruise through space to approach the Sun within 47 of its radii, while 3.7 years would be required to come as close as 34 radii.

Since the Earth circles the Sun roughly along its Equator, ground observations severely limit the view of polar regions of our home star. As a result, tilting the probe's orbital plane relative to the plane of the Ecliptic (the plane of the Earth's orbit around the Sun) would provide a unique vantage point for scientists. Russian engineers devised a five-year-long mission scenario that would place Intergelio-Zond into an orbit inclined 30 degrees toward the Ecliptic. According to Russian sources, the probe's final orbit would also be synchronized with the rotation of the Sun. (602)

A series of maneuvers in the gravitational field of Venus and Earth would be conducted in order to "slingshot" the probe onto a Sun-bound spiral. Even with the help of planetary gravity, Intergelio-Zond would still need electric engines thrusting for prolonged periods of time in order to reach its destination. According to one early concept, four solar panels with a total area of 60 square meters were designed to feed power-hungry electric engines. Upon the probe's approach to the Sun, the solar panels would swing back to hide in a shade of its thermal shield made out of tungsten, molybdenum and their alloys. Following another re-thinking of the mission, a special electrically propelled space tug from the Dvina-TM program was integrated into the design.

To resolve the contradiction between the need for huge solar panels and strict limits on the size of hardware protected by the heat shield, it was decided to discard large sections of solar panels after the delivery of the spacecraft into the vicinity of the Sun. Jettisoning the panels would also dramatically reduce the severe pressure of the solar wind onto the probe.

Scientific instruments onboard Intergelio-Zond would look at the Sun through special filtered windows in the heat shield, sending as much as 1 gigabyte of data back to Earth. (604) To stay in touch with mission control at distances as far as 250 million kilometers, Intergelio-Zond would have to use an X-band communications system, which was to be tested for the first time in the Phobos-Grunt mission. However that probe's failure to leave the Earth orbit forced a delay of the trials of X-band communications until 2014, when the Spektr-RG space observatory was to be launched into the Lagrange point behind the Earth relative to the Sun. Roskosmos also hoped to enlist ESA and NASA to provide their deep-space ground antennas for the benefit of the Intergelio-Zond mission.

The Moscow-based Lebedev Physics Institute started working on four instruments for Intergelio-Zond, which would be controlled by a single computer. The resolution of these instruments would be five times higher than that onboard of the Koronas-Foton spacecraft, Russia's previous short-lived solar observatory in the Earth orbit. According to Intergelio-Zond project scientists, for the first time, humans would get a chance to see the magnificent corona of the Sun with a resolution of just 300 kilometers and witness ejections from the polar regions of the Sun in unprecedented detail and from a unique vantage point.


In March 2009, Roskosmos announced a tender for the initial stage of Intergelio-Zond's development, allocating 25 million rubles until 2010. (The total budget for the mission was estimated at 4,200 million rubles.) As expected, NPO Lavochkin, the prime developer of the nation's planetary probes, was awarded the contract. In May 2009, NPO Lavochkin subcontracted the IZMIRAN research institute to develop some scientific payloads for the mission. A number of other leading Russian and foreign scientific centers were also expected to contribute their instruments.

By 2011, as the scientific team and its extensive array of instruments had been selected in the course of the preliminary design, the project faced a familiar problem of mass deficit. The amount of scientific payload was now quoted at 120 kilograms.

The preliminary design for the project was expected to be completed before the end of 2011.

Work in 2012

As of 2012, Intergelio-Zond was still expected to use electric engines, a protective heat shield covered with carbon-based insulation and solar panels with an active cooling mechanism in order to function in the vicinity of the Sun. However, challenges in the development of an electric propulsion system and radiation-hardened avionics pushed the launch date for the mission from the middle to the end of the decade. By August 2012, a presentation published by NPO Lavochkin quoted a launch date for Intergelio-Zond in 2019.

In October 2012, NPO Lavochkin's team defended the preliminary design of the Intergelio-Zond project at the meeting of a division of the Scientific and Technical Council, NTS, of the Russian space agency, Roskosmos. The council recommended the development of two similar spacecraft in order to increase the chances of success for the mission and to widen its scope, even though the available budget funded only a single probe.

In any case, by November, Intergelio-Zond project was cleared to proceed to a full-scale development. According to industry sources, the overcrowding of the spacecraft with science instruments could help with the decision to split the mission into two vehicles, which would allow to unload some of experiments to a backup probe. At the same time, the dual mission lifting off in two different launch windows could increase scientific return by making the same measurements from two different points or even providing stereo imagery.

In another major upgrade for the project, the much larger Proton rocket rather than Soyuz-2 was promised to be used to launch the mission.

PEP project

According to advance Russian planning, the Intergelio-Zond project could pave the way to a pair of probes known as the Polar-Ecliptic Patrol, PEP. They would be launched into elliptical orbits with a diameter of 0.5 astronomical units extending far above the Ecliptic for constant watch of the Sun and monitoring of solar activity and solar wind.

(To be continued)

Next chapter: Missions to Mercury

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Evolution of the Intergelio-Zond project:

As of...
Approaching Sun as close as 30-40 of its radii
Approaching Sun as close as 60-70 of its radii
Launch date
Launch vehicle
Spacecraft mass
8,120 kilograms
Payload mass
300 kilograms
120 kilograms


Science instruments proposed for the Intergelio-Zond mission:

X-ray telescope
Lebedev Physics Institute, Moscow
Hard X-ray telescope
Lebedev Physics Institute, Moscow
Optical coronograph
Lebedev Physics Institute, Moscow
Optical telescope
Lebedev Physics Institute, Moscow
Multi-functional optical telescope
Pushkov IZMIRAN, Troitsk
Plasma-wave magnetic detector
IKI, Moscow
Multi-channel solar photometer
Pushkov IZMIRAN, Troitsk
Ping-M (Ping-P)
X-ray polarimeter
NIYaU MIFI, Moscow
Gamma spectrometer
Ioffe FTI, St. Petersburg
Solar gamma-radiation spectrometer
NIYaU MIFI, Moscow
X-ray spectrometer
Pushkov IZMIRAN, Troitsk
Solar wind electron analyzer
IKI, Moscow
Solar wind ion analyzer
IKI, Moscow
Pushkov IZMIRAN, Troitsk
Solar wind plasma analyzer
IKI, Moscow
Radio-spectrometer and detector
Pushkov IZMIRAN, Troitsk
Charged particles telescope
Skobeltsin NIIYaF MGU
Neutron detector
Lebedev Physics Institute, Moscow


Expected budget for the Intergelio-Zond project (as of July 2008):

30 million rubles
80 million rubles
200 million rubles
1,875 million rubles
1,600 million rubles
900 million rubles
4,685 million rubles

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This page is maintained by Anatoly Zak; Last update: March 21, 2013

Page editor: Alain Chabot; Last edit: November 30, 2012

All rights reserved



In the mid-1970s, a pair of futuristic-looking US-German Helios probes flew the first dedicated mission to study the Sun from its vicinity. Copyright © 2009 Anatoly Zak


The circa 2009 depiction of the Intergelio-Zond spacecraft. Credit: IZMIRAN


The circa 2010 depiction of the Intergelio-Zond spacecraft, integrated with a Dvina-TM space tug. Credit: Roskosmos


Design of Intergelio-Zond as of 2011. The heat shield to protect the vehicle can be seen on the left. Credit: Roskosmos


Design of Intergelio-Zond as of 2012. The heat shield to protect the vehicle can be seen on the left. Credit: Roskosmos


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