Sich-2 (Optical Observation Mission-2)

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Overview

Sich-2 (Optical Observation Mission-2)

Overview    Spacecraft    Launch   Mission Status    Sensor Complement   Ground Segment   References

Overview

Sich-2 is a new-generation Ukrainian optical minisatellite mission designed and developed at the Yuzhnoye State Design Office (SDO) as the lead organization in a collaboration with the Ukrainian space industry - and within the framework of the National Scientific Research Space Program of the Ukraine. The program funding is provided by SSAU (State Space Agency of Ukraine). ^{1) 2)}

The overall objective is to obtain high-resolution imaging data in the visible and infrared region to support the following applications:

1) Monitoring of natural resources, rational nature management.

2) Agriculture, land use, town building, environment pollution monitoring and evaluation, mapping.

3) Diagnosis and forecast of technogenic and natural cataclysms (including seismic activity forecast).

4) Monitoring of ionosphere parameters.

Spacecraft

The Yangel Yuzhnoye State Design Office (SDO) has designed the MS-2 (Minisatellite-2) platform to create on its basis a spacecraft, weighing up to 200 kg, for applied or scientific missions, which operates in near-Earth orbits in the altitude range from 500 to 700 km. ³⁾

The Sich-2 spacecraft was developed as a part of the Earth observation system by SDO (State Design Office) Yuzhnoye, Dnepropetrovsk, and was built by the Industrial Association ‘Yuzhny Machine Building Plant' in cooperation with other space industry entities upon the state order of SSAU.

The MS-2 (MS-2-8 design identification) bus concept features a modular platform capable to accommodate various types of payloads within the minisatellite class and to permit various versions and modifications of the onboard supporting subsystems.

Subsystems

The MS-2 platform consists of the platform data subsystem, which includes onboard digital computer complex and telemetry module; attitude determination and control subsystem; satellite navigation equipment (GPS receiver); communication subsystem (S-band line command and telemetry instrumentation), electric power subsystem; thermal control subsystem; propulsion system (optional, depending on mission requirement); cabling and structure.

Bus Structure

The bus structure consists of instrumentation frame modules and lightweight three-layer honeycomb structures. The body structure consists of a base block and two rectangular plates, which are fastened with six tie rods, on opposite ends of the frame module cluster. The body side faces are covered with heat shields on the plates' ends. Four solar arrays are mated to one of the plates (base) by slewing mechanisms. In launch configuration, the solar arrays are folded and fastened to the mounting plate. The supporting panels of the solar arrays and the heat shields are deigned in the form of three-layer honeycomb structures, the skin of which contains carbon-filled plastic.

The Sich-2 satellite is an advanced variant of EgyptSat-1 satellite, designed by Yuzhnoye SDO, and launched on April 17, 2007. Sich-2 inherited the main elements of the payload of EgyptSat-1 (multispectral scanner, middle IR scanner, platform command & data handling subsystem, X-band communication subsystem); but instead of store & forward equipment, as on EgyptSat-1, it has a set of scientific experiments named POTENTIAL and optical angle reflectors. The Sich-2 platform is sun-oriented in standby mode; it can operate in program tilt mode (during imaging) as on EgyptSat-1.

The MS-2 platform structural features are:

• Bodies of the frame modules clusters serve as the platform body (performing load-carrying function, protecting from space environmental factors and radiation, together with heat shields).

• Inside the frame modules cluster there is the base block, a single structure with the platform's attitude determination and control subsystem instrumentation and the payload's instrumentation, which allows installing these instruments with high accuracy and ensuring instability of less than 3 angular minutes of their angular position in the orbit relatively to the platform's base coordinate system.

• The plate dimensions exceed those of the frame modules cluster, which allows installing the payload instrumentation both on external and internal surfaces of the plates around the frame modules cluster.

• The plates are located at an angle of 45º relatively to the frame module cluster, which increases the platform inner volume to accommodate the payload and at the same time decreases the platform external dimensions.

• The flight direction is realized by the body rib, which enables effective use of the heat shield radiant surfaces.

• The 3-axis spacecraft attitude and stabilization system is an active system, using magnetometer and star sensor as sensors, and flywheels and electromagnets as actuators.

• Solar arrays are not orientable; slewing mechanisms bring them in operating position at an angle of 90º relatively to the spacecraft longitudinal axis.

ADCS (Attitude Determination & Control Subsystem)

The spacecraft is 3-axis stabilized. The ADCS consists of sun sensors, magnetometer, angular velocity meters, and a star sensor, providing the determination of the spacecraft's attitude; actuation is provided by magnetorquers and reaction wheels. - In stand-by mode, ADCS ensures single-axis sun orientation of the spacecraft with an accuracy > 0.5º (7º for eclipse orbit) and angular stabilization rate <0.01º/s.

During imaging phases, the pointing of the scanners to the required target region is performed by tilting the satellite roll axis (left-to-right from nadir). The spacecraft can perform stereo-imaging within a single orbit, when the imager pointing to the required target areas is performed by tilting satellite along the pitch axis (forward-backward from nadir).

On customer's request, the platform functions and capabilities may be improved by the introduction of the following items:

• The ADCS pointing accuracy and agility may be improved with the addition of a star sensor, extra flywheels and a set of angular velocity meters, which enable the modes of S/C program rotations at angles of up to ±40º in roll and pitch and up to 3º in yaw, with an attitude accuracy increase up to 0.1º (1σ) and a stabilization of the angular velocity up to 0.005º/s.

• Use of an X-band downlink to increase the payload data rate up to 32 Mbit/s

• Addition of a propulsion subsystem to main the orbit of the spacecraft.

EPS (Electrical Power Subsystem)

The EPS includes solar panels based on single-stage GaAs (Gallium Arsenide) photo-electric cells, NiCd buffer battery, and a power conditioning unit. For a 5-year satellite lifetime, the EPS provides an average daily power ≥ 90 W (30 W for payload); a maximum power of ~405 W can be provided during a 5 minute period in the daylight phase of the orbit.

TCS (Thermal Control Subsystem)

The TCS is completely passive. The TCS includes heat shields, thermo-regulating coatings, MLI (Multi-Layer Insulation) blankets, and thermal insulators.

PCDHS (Platform Command & Data Handling Subsystem)

The PCDHS includes an ODCC (Onboard Digital Computing Complex) and a telemetry module. The ODCC consists of a computer, I/O unit with ≥ 10 serial interfaces, and a command unit with 195 control commands.

Payload Accommodation

The MS-2 platform permits to accommodate the payload both inside and outside the platform body. Inside the platform, the payload may be installed on internal surface of the base and the mounting plate (Figure 6) as well as on the base block.

On the outside, the payload may be installed on the mounting plate, considering the arrangement of antennas of the communication subsystem and the satellite navigation equipment. The total volume of payload instrumentation available inside the platform is ~ 70 dm³, and the volume outside the platform amounts to about 50 dm³ (or 50 liter).

The Sich-2 minisatellite has a launch mass of 176 kg (this includes the payload mass of 58 kg). The spacecraft dimensions in deployed configuration are: 2.38 m x 2.38 m x 1.12 m. The spacecraft design life is 5 years.

RF Communications

The TT&C data are transmitted in S-band at a data rate of 32 kbit/s. This includes also the data of the Potential instrument. The uplink frequency is 2089 MHz, the downlink frequency is 2089 MHz, MSK (Minimum Shift Keying) modulation.

The payload imagery are downlinked in X-band at a data rate of 32.72 Mbit/s. The downlink frequency is 8246.56 MHz, the modulation is OQPSK (Offset Quadrature Phase Shift Keying).

Launch

Sich-2 (as primary payload) was launched on August 17, 2011 on a Dnepr vehicle. The launch provider was ISC Kosmotras; the launch site was the Yasny Orenburg launch base, Russia. - The launch of Sich-2 was delayed several times over the last years. ⁴⁾

The secondary payloads on this flight were: ⁵⁾

• NigeriaSat-2 of NARSDA (National Space Research and Development Agency) of Abuja, Nigeria. The spacecraft was built at SSTL.

• NigeriaSat-X of NARSDA. NigeriaSat-X is the flight suitable training model of the NIGERIASAT-2 built by NARSDA engineers and a demonstration of Nigeria's capacity and capability in building future satellites of its kind in Nigeria with little or no supervision.

• EduSat of the University of Rome, Italy.

• RASAT of Tubitak Uzay, Ankara, Turkey.

• AprizeSat-5 and AprizeSat-6 of AprizeSat, Argentina built by SpaceQuest, Fairfax, VA, USA, each microsatellite features a next generation AIS (Automatic Identification System) payload. ⁶⁾

• BPA-2 (Blok Perspektivnoy Avioniki-2 — or Advanced Avionics Unit-2) of Hartron-Arkos, Ukraine. The BPA-2 experimental payload remained attached to the upper stage of the Dnepr-1 launch vehicle.

Orbit

Sun-synchronous circular orbit, altitude ~670 km, inclination = 98.26º, the orbital period is about 97.5 min, the equatorial nodal crossing time is at 10:30 hours LTAN (Local Time on Ascending Node).

Mission Status

• End of the spacecraft mission: Sich-2 stopped communicating with ground control on Dec. 12, 2012, as a result of a faulty power supply battery. The Ukrainian space agency then received 790 thousand grivnas as an insurance payment. ⁷⁾

• August 17, 2012: The Sich-2 is on-orbit for 1 year and operating nominally. So far the spacecraft has collected imagery of 4.5 million km². ⁸⁾

- The images obtained from "Sich-2" satellite have been successfully used to control the exploitation of agricultural resources, in land use and forestry, providing significant assistance in the implementation of environmental monitoring, the assessment of environmental pollution during the monitoring of emergencies and localization of their consequences, as part of mineral exploration, in course of the infrastructure projects implementation, security and defense areas etc. Space monitoring is an effective tool of public control that allows obtaining of objective information about the situation in all regions of the country.

• In 2012, Sich-2 is operating nominally providing imagery of Earth's surface in accordance with requests from the Ukrainian user community via the space system operator – Dneprocosmos State Enterprise (Ref. 2).

• The Sich-2 system was accepted by the National Space Facilities Control and Testing Center (Yevpatoriya) for trial operations and is working in design mode since December 9, 2011. ⁹⁾

• The flight tests of the Sich-2 spacecraft were completed on October 10, 2011.

• The first image from Sich-2 SC was obtained on August 25, 2011.

• Shortly after launch, the Flight Control Center (Yevpatoria) conducted the first communication session with Sich-2, received and processed the telemetry data. All spacecraft systems function normally.

Sensor Complement

The remote sensing data, received from the sensor complement, can be utilized in the interests of various socio-economic and environmental tasks. The imagery may be used for such applications as: cartography, environmental and disaster monitoring, agricultural and real-estate planning.

The two imaging instruments (MBEI and MIRS) were designed and developed at SSRE CONECS in Lviv, Ukraine, they were first flown on EgyptSat-1 as technology payloads. ¹⁰⁾

MBEI (MultiBand Earth Imager)

MBEI is a Pan (panchromatic) and MS (Multispectral) pushbroom imager providing co-registered imagery of the target area in Pan and 3 narrow MS bands within the VNIR (Visible Near-Infrared) spectral region. Some of the spectral bands are identical with those of the Vegetation instrument on SPOT missions.

The compact instrument has a mass of only 26 kg. The power dissipation of the sensors and associated driving and buffering electronics is limited to 25 W. The unit is also equipped with an additional heater of 25 W to stabilize the temperature of the instrument.

The overall objective of the MBEI instrument is to observe the irradiance coming from the soil and the vegetation. The first band (B1) is being used to make atmospheric corrections; the panchromatic channel is present to enhance the situational awareness and to ease the interpretation of the acquired data.

MIRS (Middle Infrared Scanner)

The objective of MIRS is to observe the irradiance form the target area in one SWIR (Short Wavelength Infrared) spectral band. The instrument features one optically butted module, consisting of 3 linear arrays with 500 InGaAs pixels each (Ref. 10). The SWIR detector temperature is regulated with thermal elements (Ref. 9).

This instrument is aligned with the MBEI instrument and is operated at 4 times the pitch of the VNIR bands. Due to the increased pitch, the optics is twice as small; the power of the MIRS instrument is also lower than that of the higher speed MBEI instrument.

Potential

Potential is the name of an equipment set with the objective to measure neutral and charged particles in the ionosphere. The Potential experimental equipment includes the following elements:

• Probe of neutral particles (DN probe), used for measurements of neutral particles concentration/pressure.

• Probe of charged particles (DE probe), used for measurements of charged particles concentration/temperature.

• Probe of electric field (EZ probe), used for measurements of Earth electrical field intensity within frequency range 0 to 1000 Hz.

The Potential instrumentation includes the electronic unit along with the DCPS (Data Collection and Processing System) and the PDA (Particle Density Analyzer). ¹¹⁾

The DN probe consists of two inverse magnetron converters with mutually perpendicular input gages. The DE probe is a Langmuir probe. Both devices were developed and manufactured in the ITM (Institute of Technical Mechanics) of NAS/SSAU (National Academy of Sciences / State Space Agency of Ukraine).

The electronic unit contains DCPS and the electronic parts of both PDA and the satellite body potential meter which is used to monitor the in-situ plasma. The satellite body potential meter, EZ, DCPS, and also the LEMI-016M magnetometer of the attitude control circuit have been manufactured at LC ISR (Lviv Center of Institute for Space Research) of NAS/SSAU.

DCPS controls the operation of scientific instruments, collects and processes the information received, accumulates it and forms telemetry frames data for transmission to Earth in CCSDS format and interacts with the service systems of the spacecraft according to the SSP protocol version 2.1. The DCPS was realized using the industrial component base of the world's best manufacturers of microelectronics. For example, the processor module of ODHS (Onboard Data Handling System) is based on the Atmel 32 bit processor of ARM9 architecture with a speed of up to 200 MIPS.

The successful realization of the experiment "Potential" is considered to be a valuable precursor for the follow-up large-scale experiment "Ionosat" implementation.

Optical Angular Reflector Assembly

The assembly of optical angular reflectors includes 9 elements (one reflector in the nadir direction, 8 lateral reflectors are at an angle of 60º to nadir) having operating zone – 80º cone. The reflector assembly is intended to increase the accuracy of the satellite orbital motion parameters using measurements provides by Sazhen (On-Ground Quantum-Optical System).

PCDHS (Payload Command & Data Handling Subsystem)

The PCDHS acquires the imagery, compresses (if required), and stores image data in the memory unit capacity of up to 2 GB. The PCDHS was developed at CONECS, Lviv, Ukraine.

Ground Segment

The ground segment consists of the Ground Control Complex and the Ground Data Complex as shown in Figure 17.

References

1) M. Vaisero, M. Dobrushyna, V. Kavun, S. Moskalev, A. Makarov, Y. Shovkoplyas, "Small Satellite Platform," Proceedings of IAC 2011 (62nd International Astronautical Congress), Cape Town, South Africa, Oct. 3-7, 2011, paper: IAC-11-B4.6A.12

2) Information provided by Alexander Makarov of Yuzhnoye SDO, Dnepropetrovsk, Ukraine

3) http://www.nkau.gov.ua/nsau/catalogNEW.nsf/systemE/4292067D377BB47CC2256F330055DF6E?OpenDocument&Lang=E

4) "Ukrainian Sich-2 placed in orbit," Yuzhnoye, Aug. 17, 2011, URL: http://www.yuzhnoye.com/index.php?idD=85&lang=en&id=124&path=News/News_e

5) "The national Earth remote sensing spacecraft of Ukraine will be placed into orbit by Dnepr launch vehicle as a part of 2010 cluster launch," URL:  https://web.archive.org/web/20220302234116/http://www.kosmotras.ru/en/news/79/

6) "Dnepr launches AprizeSat-5 and AprizeSat-6," SpaceQuest, August 17, 2011, URL: http://www.spacequest.com/Articles/AprizeSat_Launch_8-17-11.pdf

7) Anatoly Zak, "Sich-2," Russian Space Web, June 4, 2013, URL: http://www.russianspaceweb.com/sich2.html

8) SSAU News conference," Aug. 17, 2012, URL: http://www.nkau.gov.ua/nsau/newsnsau.nsf/HronolE/00642B1EC20EC1AAC2257A5C003BF79C?
OpenDocument&Lang=E

9) Information provided by Victor Pinyagin of Yuzhnoye SDO, Dnepropetrovsk, Ukraine

10) Oleg Lapshinov, Viktor Tkachenko, Leonid Varichenko, Jan Vermeiren, "Design, Development and First Assessment of the SWIR Instrument for Remote Sensing on Board of EgyptSat-1," Proceedings of the IAA Symposium on Small Satellite Systems and Services (4S), Rhodes, Greece, May 26-30, 2008, ESA SP-660, August 2008

11) O. L. Makarov, G. V. Lizunov, A. A. Lukeniuk, V. Ye. Korepanov, V. O. Shuvalov, Yu. A. Shovkoplias, S. I. Moskalev, "Experiment POTENTIAL onboard SICH-2 Microsatellite – First Results," Proceedings of the 63^rd IAC (International Astronautical Congress), Naples, Italy, Oct. 1-5, 2012, paper: IAC-12-B4.2.1
 

The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: "Observation of the Earth and Its Environment: Survey of Missions and Sensors" (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (eoportal@symbios.space).

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