Modernization of Nadezhda system
I. Lisov

In our December ‘98 issue, in the announcement about Nadezhda spacecraft launch, we made a mistake calling Kosmos-2315 Nadezhda-M. Actually, Nadezhda-M is an updated version of current Nadezhda (COSPAS) system that has been utilized since 1982. Proposed on-board radio system for Nadezhda is modernized to match the requirements of Cospas-Sarsat international satellite based system for search/rescue and of Russian system Kurs. On March 5, 1999, at the Russian Space Agency, a meeting of the Science-Technical Council was held. It was run by Y. Milov, assistant director of the agency. Proposals of KB Polyot and RNII KP on the satellite configuration for Nadezhda-M system were considered. Nadezhda-M system spacecraft is a satellite weighing about 160 kg with a dual purpose RK-SM payload, capable to work in both Cospas-Sarsat and Kurs control modes. The council’s decision was to come up with the rough draft of small spacecraft within 1999.

On the State of Cospas-Sarsat

Let us remind the reader that Cospas-Sarsat program started pursuant to the Soviet-American agreement on cooperation in the space field dated May 14, 1977, with accordance to the decision of the Central Committee of the CPSU and the Council of Ministers of the USSR on 'creating jointly with USA and Canada experimental satellite system for search of vessels in distress. On June 30, 1982, Soviet spacecraft (Kosmos-1383) with Cospas equipment on board was launched. Later, on September 11, it was credited with helping to save the crew of Cessna 172, Canadian airplane.

On December 8, 1987, following the flight tests of RK-S on-board of radio system tested on three spacecraft (11F643N), according to the decree No1414-350, Nadezhda was adopted for utilization. During 1989-1998, RK-C on-board radio system was installed on five spacecraft (17F118), referred to as Nadezhda in official TASS announcements.

According to the agreement among USSR, USA, Canada, and France dated July 1, 1988, USSR and USA made a commitment to have, as part of the space segment, two spacecraft with the receiver-processors and repeater units. Russia assumed the rights and obligations of the USSR in this agreement, and the decree No813 of the Government of RF dated July 3, 1997 confirmed that Cospas-Sarsat is part of the Global Sea Communications System providing security during emergency situations.

All in all, during 1982-1998, USSR and later Russia launched eight spacecraft carrying Cospas equipment; USA launched seven NOAA spacecraft carrying SARSAT equipment. Distress beacon systems were installed on 700,000 ships and planes; 20 countries have 38 ground receiving stations (Local User Terminals). Just in 1997, in 389 rescue operations, 1312 people were saved with the help of Cospas-Sarsat system. Altogether, during the lifetime of the system, more than 8,000 people were saved

To the date, three Russian and four American spacecraft, listed in the table, are operating in Cospas-Sarsat system.

Spacecraft operating in Cospas-Sarsat System

Notes:

1. The number in parenthesis is the sequence number of launched Nadezhda craft
2. Nadezhda (4) launched on July 14, 1994 was un-deployed in July 1997. Nadezhda (5), operation period of which expires in 2001, was launched to the same orbital position on December 10, 1998.

Presently, flight and exhibition tests of geostationary satellites (GOES, USA) and Insat 2 (India) using 406 MHz repeater units are completed. Launch of Luch-M, Russian geostationary spacecraft with the same equipment is scheduled at the end of 1999 and European MSG craft-in 2000. In future, Cospas-Sarsat will include two segments: geostationary and low earth orbit. Up to 2010, in the low earth orbit segment, the USA is planning to install Sarsat equipment on meteorological satellites such as NOAA and NPOESS, whereas Russia is planning to use it on small spacecraft.

Need for Modernization of Nadezhda-M Rocket Space Complex

Nadezhda was created on the base of Soviet Tsikada navigation craft. Additional payload (RK-S radio complex of Cospas system) was installed and several systems and structures were developed further. Navigation remained the priority for Nadezhda, which accounted for not always optimal, from the perspective of Cospas system, orbital location of the craft. Today, these craft became obsolete, are very costly in terms of their production, tests, and usage, and have a short lifetime. With the deployment of GLONASS, the demand for Tsikada has sharply decreased, and there have been no orders for new Nadezhda craft since 1995. The factory-producer has two modernized craft for Nadezhda-M system.

Launched craft are controlled with the old, outdated computers (M-222) and Taman-Baza DM control-measurement system, which goes against the decisions allowing to operate the system only up to 1995.

Modernization of Nadezhda system was specified in the decree dated 1987 and in the resolution No8 dated January 11, 1990, of Military Industrial Complex attached to the Council of Ministers of the USSR. The purposes of the project included expansion of the range of functions, improvement of distress location accuracy, improvement of interference shield and distress information transmission. However, this resolution provided for an insignificant modernization of spacecraft for installation of modern RK-SM on-board radio complex.

Currently, with limited financing, modernization of the rocket space complex of Nadezhda system is an important international obligation Russia has to fulfill before 2010. That is why, on February 7, 1999, the Director General of the Russian Space Agency signed the decree that provided for creation of specialized craft for Nadezhda-M space system.

Experimental Works

The result of the scientific-research project "Spasenie-XXI" ("Rescue-XXI), undertaken by RNII KP and KB Polyot and directed at modernization of the space segment of Nadezhda system, was the creation of small, specialized spacecraft, based on the modern principles of small craft building, their development, testing, and control. Development of dual-purpose system, used for location of distress beacons as well as for location of mobile objects and collection of data transmitted from these objects, creates additional demand for Nadezhda-M and partly covers its maintenance costs. For this purpose, at RNII KP, a second generation, dual mode, on-board radio complex RK-SM was designed.

Development of small spacecraft for Nadezhda-M system at KM Polyot was based on the experience gained during the R&D oriented at designing small spacecraft and microsatellites for communications solutions, information transmission, etc. All technical solutions of service system complex tasks were tested on Cosmos-2285 small spacecraft (deployed on September 23, 1994) and 21KF2 microsatellite (FAISat-2V deployed on September 23, 1997 as an additional payload for Cosmos-2346 [5]).

Specifically, a building principle and algorithm of one-axis solar orientation operation of spacecraft in combination with gravitation attitude control.

Exploitation of 21KF2 spacecraft confirmed the principle of spacecraft building without pressurized container. Magnet-gravitational attitude control system was developed (gravitation boom and electromagnet device (instead of passive magnet dumper use on Cosmos-2285) in particular).

Developments in navigation and frequency/time support were tested on 21KF2 and Zeya microsatellites. The latter was deployed on March 4, 1997 by Start-1.2 launcher from Svobodniy cosmodrome).

It is noteworthy that 21KF2 was actually the prototype of a small spacecraft of Nadezhda-M system. But instead of rescue mission equipment it had repeater units, produced by the American company Final Analysis. All the fuss around deployment of FAISat-2V, publications about the reconnaissance mission of the satellite (see footnotes in [4]), as we see it, could have been inspired by both American and Russian competitor-companies. Development of Kurs system started in 1985 on the base of Cospas system [5]. Kurs-E experimental equipment was first installed on Cosmos-2315 (Tsikada-M), deployed on July 5, 1995 [6]. Modernization of equipment and software of ground receiving stations (LTU-1,-2,-3), which allowed their use in Cospas as well as in Kurs systems, was undertaken in 1992. Flight tests of Kurs system were completed in October 1996. From 1997 it has been used by the Ministry of Transport for experimental purposes. In July-August 1998, during KSOUN-98 training in the Finnish Gulf, MARAN beacon was installed on the ship belonging to the Federal Frontier Service. Accuracy of the ship's location determination using Kurs system was 1.5 miles better. In fall 1997-1998, cranes' movements were tracked using miniature 90 g beacons designed by RNII KP. Kurs-E equipment is expected to operate until 2002.

Potential customers of Kurs system include Federal Frontier Service, State Customs Committee and other departments. However, all of them demand an increase in daily number of objects location, which is impossible without an increase in number of spacecraft in the system.

Assumed Characteristics of Nadezhda-M Small Spacecraft

Small spacecraft of Nadezhda-M system is intended for receiving, storing, and transmission of information to LUTs from beacons located on air and naval craft, transport, etc. On-board radio complex has to simultaneously service not less than 150 objects located in the zone of radio visibility, to store information on not less than 2000 objects during one revolution, and to have a lifetime not shorter than five years.

Underlying the small spacecraft project of KB Polyot are several principles that have never or seldom been used on Russian spacecraft. Small spacecraft has folding, non-thermostatic solar battery panels, combined channels for receiving and transmitting mission information, and a modern base of elements in the on-board control complex, which includes receiver unit of GLONASS system.

The mass of small spacecraft is around 160 kg (mass of Nadezhda craft is around 850 kg). The body has a shape of a prism with a height equal to 1000 mm and the height of the side facet equal to 450 mm. The angle at the acute tops is equal to 60 degrees. The shape of the body was chosen taking into consideration the size of the additional payload during the accompanying launch.

Functionally, the craft is divided into payload (RK-SM) and complex of service systems.

Modernization of the receiver-processor of RK-SM took the following forms: increase in number of simultaneously serviced distress radio beacons-406 (DRB-406) from 70 to 150 with the extension of the bandwidth from 25 to 80 kHz, introduction of the receive and process mode of Kurs system beacon signals (with 405.928 MHz frequency) in the range of ± 40 kHz. RK-SM provides:

In Cospas mode:

In Kurs mode:

RK-SM has three channels of signal processing, in the 405-406 MHz range. Sensitiveness of signal reception from DRB-406 and RM-405 constitutes -162 DB/W, mean square root error of 0.3 Hz Doppler frequency measurement. The memory capacity of frame forming device is 0.5 Mb in Cospas mode and 2.0 Mb in Kurs mode.

The possibility of Cospas and Kurs combined operation is being considered. Transmission of commands to the board would be done in 405.90 or 406.22 MHz frequency ranges at 400 b/sec.

The mass RK-SM is 55.2 kg and its power consumption in an unstopped mode is 62 W. Radio complex has one low gain receiving antenna (121.5 MHz), one for 405/406 MHz range, and one transmitting low gain antenna for 1543/1643 MHz range.

The service systems complex of small spacecraft designed by KB Polyot includes on-board control complex (OBCC), combined three-axis attitude control system, power supply system, thermal control system, and mechanical systems.

OBCC provides: operational control of small spacecraft, autonomous control of equipment and systems (up to 30 days), transmission of telemetric information, navigation solutions for GLONASS/GPS system signals, formation and synchronization of on-board time standard, formation of base frequency, attitude control and other functions. OBCC includes on-board control system (OBCS) (based on DOKA-15-B, equipment designed by NIL AKT) and control block designed by KB Polyot.

Combined three-axis attitude control system provides the error of spacecraft longitude axis orientation relative to local vertical or perpendicular orientation relative to Sun-spacecraft-Earth plane not worth than ± 5^o. The system includes the main and reserve three-axis magnetometer, controlling reaction wheel, 4.5 meters gravitation boom, three electromagnet devices, and Polyot-MK control software.

In orbit, magnetometers and electromagnet devices are started during separation period. Dumping and attitude control of small spacecraft relative to earth magnetic field lasts five hours. Next, gravitation boom slides out and solar orientation mode with the controlling reaction wheel turns on. When the desired attitude is reached, the solar battery panels unfold.

Power system provides power level at the end of lifetime equal to 120 W (voltage-27 V). System includes solar battery (six panels, with two unfolding ones) designed at NPO Musson with the solar devices, NiH 28NV25 battery with 27 A x hr capacity designed by NPO Saturn or NIAI, complex of automated mechanisms and stabilization designed by NPO Pulsar, and on-board software.

Thermal control system provides temperature control for on-board equipment in the range of -10…+40^oC. This equipment includes temperature devices, MLI, thermal shunts, etc.

The main structure represents an equipment frame with devices, cable network, screen-vacuum thermal insulation, and mechanical systems of small spacecraft. In the lower part of the frame, BRK EA171 equipment, control reaction wheel, on-board chemical battery, and three spiral antennas are installed; in the upper part--BRK EA172 equipment, GLONASS/GPS navigation equipment, gravitation boom, three electromagnetic devices, three compensators, and three pin antennas.

Orbital Constellation and Ground Complex

Modernization of Nadezhda system provides for changes in orbital parameters of small spacecraft. Currently, Cospas and Sarsat use orbits of various attitude and inclination, which leads to relative displacement of the planes and periodic emergence of zones with a long spacecraft waiting period. Due to the fact that the navigation part of Nadezhda-M will not appear on small spacecraft and in the interests of potential Kurs system users, there is a possibility to deploy the craft to sunsynchronous orbits with the 98^o inclination and 830 km altitude. These orbits are used by NOAA craft with Sarsat payload. Spacecraft of both countries will be located in four orbital planes with fixed relative positioning of ascending nodes.

Ground mission control system of spacecraft should include a station--that transmits command and receives telemetric information (SPPI)--combined with the mission control sector. This station is advisable to create on the base of the LUT of second generation Cospas-Kurs system. Mission control sector should provide consequent control of not less than three small spacecraft. It exchanges telemetric and command-program information with the computer system of Cospas-Sarsat, to which LUT-2 (Arkhangelsk city) and LUT-3 (Nakhodka city) are connected. They exchange distress information with Cospas-Sarsat computer system. To determine the orbital parameters, measurements of Doppler shift in the radio link of spacecraft SPPI or in radio link between small spacecraft and special 'orbital-graphic' distress beacons are used. These distress beacons are ground beacons that transmit high stability signals and have specific coordinates.

First launch of small spacecraft of Nadezhda-M system can take place 12-18 months after the start of the project financing.

Sources:

1. Nadezhda--My Earth Compass…, Novosti Kosmonavtiki, n1, 1999, pp. 47-48
2. Informational Bulletin of Plesetsk cosmodrome press-center, n.38, November 10, 1994
3. Information on Cospas-Sarsat system, n23, February 1999, Cospas-Sarsat Secretariat edition, London
4. Cosmos-2346 and FAISat-2V Satellites Launched, Novosti Kosmonavtiki, n20, 1997, pp.40-45
5. Kurs-system Tests Have Been Completed, Novosti Kosmonavtiki, n12, n13, 1996, pp.49-52
6. Cosmos 2315 Launched, Novosti Kosmonavtiki, n14, 1995, p.31