Pages 549-557


L.M.Zelenyi1, P.Triska2, and A.A.Petrukovich1

1Space Research Institute, Russian Academy of Sciences, 84/32 Profsoyuznaya st., Moscow, 117810, Russia ,
2Institute of Physics of Atmosphere, Academy of Sciences of Czech Republic, 11 Bocni, Praha 4, Czech Republic


INTERBALL-1 spacecraft with the subsatellite MAGION-4 was launched on August 3, 1995 to the highly elliptical orbit with the period of 92 hours and apogee 193000 km. Both spacecraft carry onboard the full spectrum of scientific instruments for the plasma investigation. The separation of two spacecraft varies from 100 to 10000 km. Such a distance permit to study spatial extents and velocities of the variety of large-scale and small-scale magnetospheric structures. INTERBALL-2 spacecraft, complementing the first pair on the auroral orbit with the period about 6 hours and apogee 19200 km, was launched at the 29th of August, 1996.


Initial idea of the multi-point INTERCOSMOS mission had its roots at the middle of 70-ties approximately at the time of ISEE-1/2 dual probes. Originally it was planned that soon after "Intershock" (PROGNOZ-10), launched in April, 1985, pair of next "PROGNOZ" type spacecraft will be launched to explore auroral and tail regions of the Earth's magnetosphere. Unfortunately, path of "INTERBALL" was much more thorny than all of its predecessors. Dramatic changes in Soviet Union and Eastern Europe during last decade result in numerous delays of the mission. Finally Tail Probe (INTERBALL-1) was launched on August 3, 1995. Auroral Probe, also after a number of delays, was launched at the 29th of August, 1996.

It is interesting to note that the name of the mission INTERBALL has an imprint of the time (1976-1977), when the mission was originally thought off. The older generation of magnetospheric scientists remembers the fascinating discussions of magnetotail Fireballs very popular at that time (Frank et al., 1976). First part of the name of the mission "INTER" was motivated by the very wide international participation in its scientific payload. The list of foreign participants of INTERBALL also experienced many changes during this complicated decade. Currently it includes Austria, Bulgaria, Hungary, Great Britain, Germany, Greece, Italy, Canada, Kirgizia, Cuba, Poland, Romania, Slovakia, Finland, France, Ukraine, Uzbekistan, Czech Republic, Sweden, European Space Agency (countries are ordered according to russian alphabet). Recently US, Japanese and Chinese scientists also joined to the analysis of INTERBALL data. Unfortunately, it is hard to expect that the future of the mission will be unclouded. Lack of budgeting for spacecraft operations already resulted in substantial data gaps during summer 1996 Tail Probe measurements at the day-side magnetosphere. However, INTERBALL community keeps a reasonable optimism about the future of the programme.

A number of interesting results already obtained from September 1995 to June 1996 by INTERBALL experimentators will be partially presented at other INTERBALL and IACG papers at this volume.


Scientific objectives of the mission are twofold -- to study the global dynamic characteristics of the magnetospheric processes as well as small scale features of these processes at the key plasma regions of the Earth's magnetosphere and its neighborhoods. Accordingly, mission was tailored as 2+2 system, which includes two pairs of spacecraft at highly elliptical, polar orbits. International group for ground based observations also is working as an important part of the project.

First pair (Tail Probe) consisting of main spacecraft (modified PROGNOZ type) and its subsatellite (MAGION-4) has an orbit with 193000 km apogee, low perigee (which evolves from 800 to 2000 km), 62.8° inclination and orbital period 92 h. The orbital characteristics are optimized in such a way that the spacecraft crosses the magnetotail neutral sheet at the distance 8-15 Re from the Earth. At some orbits INTERBALL-1 is moving nearly along the neutral sheet for several hours (Figure 1) granting a unique possibility to perform thorough studies of this key magnetotail region. As a consequence, INTERBALL-1 observes high-latitude magnetopause on the outbound part of the orbit and low-latitude magnetopause and boundary layer on the inbound part (Figure 2).


Figure 1: Model neutral sheet (Fairfield, 1980) crossings by INTERBALL-1 during the magnetotail campaign 1995/1996 (GSE frame). Squares indicate moments of crossing. Squares are repeated each hour and connected by a line if the crossing lasts longer than one hour.


Figure 2: Prediction of the magnetopause crossings for the INTERBALL-1 first year of operation in two projections (GSE frame of reference). Magnetopause model by Sibeck et al (1991) is used.

Figure 3: INTERBALL-1 and MAGION-4 separation at the distance 100000 km from the Earth center. The curve is connecting monthly points.

Auroral pair consisting of PROGNOZ and MAGION-5 spacecraft was launched at the end of August, 1996. It's orbit has an apogee 19200 km, perigee 750 km, inclination 62.8° and orbital period 5 h 47 m. In the future the measurements in the tail and auroral regions hopefully will be supplemented by the data of the plasma package at astrophysical Relict-2 spacecraft which will operate at L2 -- Halo orbit. The relative position of the orbits of Auroral and Tail probes is selected to optimize possible conjunctions between them, i.e. to maximize the time satellites spend simultaneously in the vicinity of the same auroral flux tubes. Main scientific instruments onboard Auroral Probe are functioning normally although at the moment of preparation of this manuscript some of them are still in commissioning phase. Unfortunately, during the first days of MAGION-5 operation due to malfunctioning of some parts of battery charging system it was discharged and up to now MAGION-5 is not responding to commands from the ground.

INTERBALL-1 subsatellite has a maneuvering capability and the separation for this pair might be adjusted accordingly to the spatial scale of physical processes under study in the range 100-10000 km. Actual separation between Tail probe and its subsatellite at the distance 100000 km from the Earth during the first year of INTERBALL-1 operation is shown in Figure 3. For the second year this separation will be increased by 30-40%.


Key characteristics of the INTERBALL spacecraft, designed and controlled by Lavochkin association and manufactured by this association and other Russian institutions are shown in Table 1. (Numbers in brackets refer to the Auroral Probe -- INTERBALL-2).

Subsatellites have been designed and manufactured in Czechia with the assistance of Russian and Austrian specialists. Main technical characteristics of MAGION-4 spacecraft are listed in Table 2. Scientific payload of the Tail probe and its subsatellite (MAGION-4) designed and manufactured in 20 participating countries is briefly described in Tables 3 and 5. Scientific payload of the Auroral probe is summarized in Table 4.

This payload enables to conduct measurements of:
(a) Fluxes of Solar wind and magnetospheric plasma, ion and electron distribution functions, plasma composition in wide range of energies.
(b) Electric and magnetic fields.
(c) Plasma waves.
(d) Solar radio and X-ray emissions.
(e) UV Auroral emissions.

The detailed description of scientific payload might be found in INTERBALL pre-launch report (CNES, 1995, distributed on request) and in a series of first INTERBALL publications submitted to Annales Geophysicae (1996). Unfortunately, due to malfunctioning of few experiments there are some differences between the actual list of operating INTERBALL-1 instruments (Table 3) and the pre-launch report.


Table 1: INTERBALL-1 (INTERBALL-2) S/C Characteristics

S/C Type

Spacecraft/scientific payload mass

Subsatellite mass

Power consumption

S/C size


1250(1370)/250(370) kg

59.5(68) kg

250 W

Diam. 2.3m, height 5m, booms 22m x 15m

S/C orientation

S/C stabilization

Pointing accuracy/knowledge

constant Solar

spin stabilized at 0.5 rpm

10° / 0.5°

Service/scientific memory
(Scientific memory is designed in IKI)

Service/scientific telemetry

STO telemetry (direct transmission)

Receiving stations

Main spacecraft/subsatellite and STO

Communication sessions

30/680 Mbit

16/64-125 Kbps

-( 40kbps)

Evpatoria/Panska Ves

Once in 2-4 days


Table 2: MAGION-4 Characteristics


Attitude sensors

constant solar, accuracy ± 15° /spin stabilized 0.5 rpm

solar and horizon sensors , magnetometer


Digital telemetry

Analog telemetry

Telecommand link

Digital memory

Programmer (onboard timer)


bands: 137, 400 and 1530 MHz, power 1.2-5 W

max. 40 kbit/sec., re-programmable

broadband 100 Hz - 60 kHz, sub-carriers 0.01 Hz - 1.3 kHz

Bands: 150 MHz and 450 MHz, 1028 direct commands

32 Mbit

8 kByte capacity ( 2600 programmed commands)

Voltages, Currents, Status, Temperatures etc (272 items)




pressurized gas system, total impulse 25 kg.sec

Solar array 32 Watts, NiCd Battery 2x 12 V/4Ah

59.5 kg


Table 3: INTERBALL-1 Instrument Summary

Instrument PI Description
Ground-based V.Sergeev PC index, etc
SCA-1 O.Vaisberg Fast 3D measurements of ions, 0.05-5 keV/Q
ELECTRON J.-A.Sauvaud 3D electron measurements, 0.01-30 keV
VDP J.Safrankova Omni-directional plasma sensor (Faraday cup), 0.2-2.4 keV
CORALL Y.Yermolaev 3D ion energy distribution, 0.025-25 keV/Q
PROMICS-3 I.Sandahl 3D ion energy distributions and mass composition, 0.004-30 keV/Q
ALPHA-3 V.Bezrukikh Thermal plasma ion flux (ion trap), Ni> 1   cm-3, E < 25 eV/Q
DOK-2X K.Kudela Energetic electron and ion spectrometer, e: 20-400 keV, i: 20-850 keV
SCA-2 E.Morozova


High energy particles anisotropy and composition

e: 40-500 keV, p, : 50 keV/n -150 MeV/n

RF-15I O.Likin Solar X-ray Photometer, 2-200 keV










Wave and field experiment

Flux-gate and search-coil magnetometers, 0-2000 Hz

Waveform processor

Flux-gate magnetometer, 0-32 Hz, ±128 nT

Electric field experiment

FM-3I M.Nozdrachev Flux-gate magnetometers, a: ±200 nT, b: ±1000 nT
AKR-X V.Grigorieva AKR receiver, 100-1500 kHz


Table 4: INTERBALL-2 Instrument Summary

Instrument Description
SCA-3 Energy-angle distributions of electrons and ions, 0.03-15 keV;

TOF for M=1,4,16, 30-500 keV

ION 3D electron and ion measurements, M=1,2,4,16; 0.005-20 keV/Q
PROMICS-3 3D ion energy distributions and mass composition 0.004-30 keV/Q
HYPERBOLOID 3D ion measurements and composition, 0.1-80 eV
KM-7 Temperature of thermal electrons, T  10 eV
ALPHA-3 Thermal plasma ion flux (ion trap), Ni> 1 cm-3, E < 25 eV/Q
DOK-2A Energetic electron and ion spectrometer, e: 20-400 keV, i: 20-850 keV
MEMO Wide-band Electro-magnetic wave analyzer,  240 kHz
POLRAD Auroral Kilometric Radiation Receiver, 20-2000 kHz
IESP-2M DC and ULF electric field experiment, 0-30 Hz
NVK-ONCH VLF electro-magnetic wave analyzer, 20 Hz - 20 kHz
IMAP-3 Triaxial flux-gate magnetometer, 0-10 Hz, ±70000 nT
RON N+2 ion source, s/c potential control, 0-15 µA
UVAI UV auroral imager, 140-160 nm
UVSIPS UV auroral spectrometer, 130.4 and 135.6 nm


Table 5: MAGION-4 Instrument Summary

SGR-8 Three-axial flux-gate magnetometer
ULF Four channel waveform analyzer, 0.01-30 Hz
KEM-3 One component electric dipole 0.1 Hz -400 kHz

3 axes search-coils, 0.1-1300 Hz

1 axis search-coil, 100 Hz - 45 kHz

SAS Step Frequency Analyzer, 2 channels 32 Hz - 2 kHz

or 0.4-20 kHz and 1-400 kHz

VDP-S Four ion Faraday Cups, 10-12-10-10 A
DOK-S Energetic electron and ion spectra, 20 keV - 1 MeV, 2 directions
MPS/SPS Electron and proton electrostatic analyzers, 50 eV - 20 keV, 3 directions
RF Solar X-ray photometer, 1.5-500 keV


The goal of the INTERBALL-1 Key Parameter (KP) preparation is to provide fast and reliable presentation of the basic physical parameters measured within the project (Table 6). Parameters are supplied with the instrument status flags. They are formatted in the CDF and ASCII files and plotted in the GIF format. KP are calculated with the 2-3 week delay after the raw data becoming available at the INTERBALL data center. Full description of the INTERBALL-1 Key Parameters can be found on the WWW homepage ( KP can be obtained via the FTP interface from IKI RAN.

The Polar Cap geomagnetic index is included in the INTERBALL Key Parameter data set. It is supplied by the ground-based measurements team of INTERBALL project headed by V.Sergeev.

An example of the INTERBALL-1 KP for the first half of August 29, 1995 is in Figure 4. Data from the magnetic field instrument MIF-M/PRAM and electron spectrometer ELECTRON are presented. INTERBALL-1 begins this day in the solar wind, then at 2:20 UT bow shock, and at 9:00 UT magnetopause are observed. At the moment of the magnetopause crossing is detected, the sharp peak produced by hot electrons is present (electron energy panel).

All INTERBALL participants have free access to all KP from all mission experiments. For the selected time intervals (e.g. IACG campaigns) INTERBALL KP are available to all or part of the scientific community. After three years all KP will have free access. KP are intended mainly for planning, event selection and preliminary studies. Explicit use of the KP data in the publication must be agreed with the PI at an early and appropriate time.


Figure 4: INTERBALL-1 Key Parameters for the 29th of August, 1995. From top to the bottom: magnetic field total value (MIF-M/PRAM experiment), electron density and mean energy (ELECTRON experiment). Bow shock crossing is at 2:20 UT. Magnetopause crossing is at 9:00 UT.


Table 6: INTERBALL-1 Key Parameters

Parameters Experiment Resolution
INTERBALL-1 coordinates and velocity 1 hour
Polar Cap index, Vostok and Thule Ground 5-15 min
Magnetic field vector MIF-M/PRAM 2 min
Electron density, mean energy, 0.012-26 keV ELECTRON 2 min
Fluxes of energetic particles:

Electrons 21-26, 76-95 keV; ions 22-28 keV

Electrons 150-500 KeV; ions 1-3 MeV



2 min

2 min
Ion composition 1.0-30 Kev, H+, O+ count rates PROMICS 1 spin
magnetic wave spectral amplitudes, 1-4, 600-850 Hz

radio-intensity flux, 100, 252, 500 kHz



2 min

2 min

Ion density, velocity vector, temperature, 0.025-25 KeV CORALL 1 spin
Antisunward total ion flux VDP 2 min


One of the specific features of the INTERBALL-1 project is the possibility to perform two point measurements with the help of the subsatellite MAGION-4. During the August 1995 - May 1996 the separation distance was about 500-5000 km at the 100000 km altitude (Figure 1). Such a separation permits to measure velocities and thicknesses of large-scale structures and magnetospheric boundaries (see Subsec 5.1, 5.2). However, this distance is too small to track reliably motion of the magnetotail structures (Subsec 5.3). Separation of order of 100 km in June 1996 will help to investigate small scale structures and plasma waves near the magnetospheric boundaries. Three examples of dual satellite magnetic field measurements near the magnetopause, bow shock and magnetotail current sheet are presented in the next subsections. Crossings are selected to be single and with the clear field reversals to reach higher confidence in the velocity determination. Boundaries are supposed to move along their normals and velocities of these motions are assumed constant. Characteristics of all crossings are in Table 7. MIF-M/PRAM (INTERBALL-1) and SGR-8 (MAGION-4) magnetic field instrument data are used in the current study.


Table 7: Characteristics of the Crossings

Date 02.09.95 05.03.96 01.11.95
S/C Coords, RE

S/C Velocity, km/s*

local normal

separation, km*

relative velocity, km/s*

-3.9, -8.5, 13.2


.34, -.46, .81



3.8, 22., 0.27


.65, .75, .08



-9.6, -6.8, -1.1


1., 0., 0.



*'+' means outward direction, '-' - inward direction.

5.1.High Latitude Magnetopause Crossing 02.09.95

The outbound magnetopause crossing by the main spacecraft occurred at 18:46 UT (Figure 5). During the next 15 minutes up to 19:00 the transition layer is observed with the variable magnetic field and modified magnetosheath plasma. After 19:00 UT usual magnetosheath is observed. The magnetopause normal is computed with the help of the model, proposed by Sibeck et al (1991). The boundary is supposed to move along its normal. The time shift between steps in the Bx magnetic field components is 83 sec. That corresponds to 6.8 km/s of relative velocity. Size of the transition layer then is about 6000 km.

Figure 5: INTERBALL-1/MIF-M (solid line) and MAGION-4/SGR-8 (dotted line) GSE magnetic field Bx component for the magnetopause crossing. Magnetosphere is on the left. Subsatellite curve is shifted 20 nT down for better viewing.

5.2.Oblique Bow Shock Crossing 05.03.96

The oblique (bn=50°) supercritical (Ma  8) bow shock was registered at 14:00 UT (Figure 6). Again, the shock front is assumed to move along its normal. The normal computed with the help of the minimum variance analysis is just 10° apart from the normal computed with the help of Fairfield shock front model (Fairfield, 1971). The comparison of the magnetic field total values measured onboard INTERBALL-1 and MAGION-4 gives the delay of 135 sec and relative velocity of the shock front inward motion of 13.8 km/s. The enhancement of the magnetic field total value upstream the ramp, which lasts about 100 sec have then the thickness of order of one ion gyro-radius.


Figure 6: INTERBALL-1/MIF-M and MAGION-4/SGR-8 (in the upper right part) magnetic field total value for the bow shock crossing. Solar wind is on the right.

5.3.Current Sheet Crossing 01.11.95

During November 1, 1995 both INTERBALL spacecraft were approaching the Earth nearly in the equatorial plane and along the magnetotail axis. The Bx GSE component of the magnetic field is in Figure 7. According to the prediction of the Fairfield neutral sheet model (Fairfield, 1980) spacecraft must be inside the neutral sheet from 19:00 to 22:00 UT. Low values of the Bxcomponent are really observed from 18:30 to 21:00 UT. At 21:00 sudden dipolarisation is observed. Thirty minutes after Bprofile returns to the prediction of the geomagnetic field model. The goal of the dual spacecraft data analysis was to determine the projection of the propagation velocity of this dipolarisation jump on the magnetotail axis. Unfortunately, insufficient resolution of MAGION magnetic field experiment data, available up to now, permitted only to estimate the lower limit of this velocity, which is equal to 200 km/s.


Figure 7: INTERBALL-1/MIF-M (solid line) and MAGION-4/SGR-8 (dashed line) GSE magnetic field Bx component for the magnetotail crossing.


In the second year of the INTERBALL-1 operations the emphasis will be done on the correlative with the Auroral Probe (INTERBALL-2) studies in the magnetotail. Inter-Agency Consultative Group for Space Physics decided to extend for the second year (1996/1997) Joint Campaign 1: Magnetotail energy flow and nonlinear dynamics. INTERBALL-1 and -2 experimental teams therefore are expecting to continue very interesting and important correlative studies with GEOTAIL, WIND, IMP-8 spacecraft and looking forward for the new exciting possibilities in the multi-mission studies which appeared in 1996 after the launches of POLAR and FAST.

We also hope that RELICT-2 launch in the nearest future will complement international plasma science fleet in the L2 halo point.


Authors are grateful to the Dr. Chiobanu and Dr. Romanov for the MAGION-4 and INTERBALL-1 magnetic field data. Orbital data are prepared by Dr. V.Prokhorenko and Prof. N.Eismont.


Fairfield D.H., Average and unusual location of the Earth's magnetopause and bow shock, J. Geophys. Res., 76,
6700 (1971).

Fairfield D.H., A statistical determination of the shape and position of the geomagnetic neutral sheet, J. Geophys. Res., 85, 775 (1980).

Frank L.A., Ackerson K.L., and DeCoster R.S., On the hot tenuous plasma fireballs and boundary layers in the
Earth's magnetotail, J. Geophys. Res., 81, 5859 (1976).

INTERBALL mission and payload , IKI-CNES (1995).

Sibeck D.G., Lopez R.E., and Roelof E.C., Solar wind control of the magnetopause shape, location and motion,
J. Geophys. Res., 96, 5489 (1991).