Space Brief 27 Feb 2025
Today's highlights include Rocket Lab's progress on the Space Force's VICTUS HAZE mission, BlackSky's new government contract, and AEI's policy recommendations for Space Force restructuring.
ISS (ZARYA) (25544)
COSPAR: 1998-067A | Alt Name: Zarya (FGB)
Image
Additional Sources
Launch Details
Launch Date
November 20, 1998
Launch Site
Launch Pad
LC81/23
Launch Vehicle
Proton-K (8K82K)
Orbital Elements
NORAD ID
25544
International Designator
1998-067A
Epoch
Sat, 04 Jul 2026 02:07:57 GMT
Apogee
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Perigee
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Inclination
51.63°
Right Ascension
216.43°
Eccentricity
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Argument of Perigee
253.07°
Period
92.97 min
Mean Motion
15.49 rev/day
Latitude
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Longitude
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Altitude
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Velocity
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Polar Plot
3D Visualization
Basic Satellite Info
Name
ISS (ZARYA)
Alternative Name
Zarya (FGB)
Type
Payload
Status
Operational
Owner
NASA
Country
USSR/Russia
Constellation
N/A
Related Satellites
Major Events
1994-12: Construction begins at Khrunichev (KHRU) in Moscow. 1998-01: Construction completed. 1998-11-20: Launched on Proton-K from Baikonur (TYMSC, LC81/23) at 06:40 UTC. Inserted into 220 x 340 km orbit. 1998-11-25: Maneuvered to 383 x 396 km orbit awaiting STS-88. 1998-12-04: STS-88 (Endeavour) attaches Unity (Node 1) module. 1998-12-13: STS-88 departs; Zarya autonomously manages ISS power, propulsion, and guidance. 1999-05: STS-96 outfitting and reboost visit. 2000-05: STS-101 outfitting and reboost visit. 2000-07-26: Zvezda Service Module docks to Zarya aft port. Zarya main engines permanently disabled; propellant tanks repurposed for Zvezda fuel storage. 2000-11-02: First permanent crew (Expedition 1) arrives. 2007-08-14: Zarya passes 50,000-orbit mark during STS-118. 2021-07-29: Nauka (FGB-2, the backup flight spare) launched and docked to ISS. 2028: FGB propulsion system certified for continued operation through this date.
Latest TLEs
1 25544U 98067A 26185.08885440 .00007564 00000-0 14587-3 0 9999
2 25544 51.6303 216.4301 0006763 253.0749 106.9498 15.48879284574378
Source: Celestrak
Summary
ISS Zarya (Functional Cargo Block / FGB), also known by its serial number 77KM No. 175-01, is the first module of the International Space Station. Funded by NASA under a $220 million contract but built by the Khrunichev State Research and Production Space Center (KHRU) in Moscow under subcontract from Boeing, Zarya's design traces directly to the TKS spacecraft developed for the Soviet Salyut programme and the 77KS modules that formed the core of Mir.
Launched on November 20, 1998, at 06:40 UTC from the Baikonur Cosmodrome (TYMSC, LC81/23) aboard a Proton-K rocket, Zarya was inserted into a 220 x 340 km orbit at 51.6° inclination and subsequently maneuvered to ~386 km circular orbit. The module measures 12.56 m in length, 4.11 m in diameter, and 23.9 m span with deployed solar arrays. It has a mass of 19,323 kg.
Zarya provided the station's initial propulsion, power, and guidance. Its propulsion system includes two 417 kgf main engines (permanently disabled after Zvezda docking), 24 large steering jets (40 kgf), and 12 small steering jets (1.3 kgf), fed by 16 external fuel tanks with a total capacity of over 6 tonnes of propellant. Power comes from two deployable solar arrays (10.67 x 3.35 m each) and six NiCd batteries providing an average of 3 kW. The module has three docking ports and uses the Russian Kurs automated rendezvous system.
Zarya autonomously managed the station for nearly two years before the arrival of the Zvezda Service Module in July 2000, far longer than the originally planned six to eight months. After Zvezda docking, Zarya's main engines were permanently disabled and its role shifted primarily to internal and external storage, with its fuel tanks repurposed for propellant transfer to Zvezda. The FGB propulsion system has been certified for continued operation through 2028 via a comprehensive life extension test campaign.
Zarya has far exceeded its 15-year design lifetime, remaining a functional part of the ISS past 27 years on orbit. A flight spare, FGB-2, was completed as the Nauka module and launched to the ISS in July 2021.
Physical Characteristics
Length
12.56
Diameter
4.11
Span
23.9
Dry Mass
19323
Launch Mass
19323
Shape
Cyl + 2 Pan
Radar Cross Section
399.0524
Visual Magnitude
Unknown
Color
Unknown
Material Composition
Aluminum alloy primary structure.
Technical Details
Payload
Functional Cargo Block (FGB), serial 77KM No. 175-01
Purpose
First ISS module providing initial propulsion, power, and guidance. Propellant storage for ISS Russian Segment (16 external fuel tanks, 6+ tonnes capacity). Internal pressurized storage. Docking adapter between US and Russian ISS segments. Attitude control during early ISS assembly (24 large + 12 small steering jets). Now primarily used for storage and propellant transfer to Zvezda.
Mission
Space station
Manufacturer
KHRU
Life Expectancy
15 years design life. Still operational as of March 2026, exceeding 27 years on orbit. FGB propulsion system life extended to 2028 via comprehensive test campaign.
Bus
77KS
Configuration
77KM No. 175-01
Motor
2 main engines (417 kgf each, turbopump-fed, regeneratively-cooled) — permanently disabled after Zvezda docking. 24 large steering jets (40 kgf each). 12 small steering jets (1.3 kgf each). 16 external fuel tanks (total capacity 6.1 tonnes propellant). 16 pressurant tanks.
Equipment
3 docking ports (1 aft, 2 on forward docking sphere — forward and nadir). 16 external propellant tanks (6.1 tonnes total capacity). Kurs automated rendezvous and docking system. Communications antennas. Pressurized cargo storage (46.7 m³ habitable volume).
Power System
2 deployable solar arrays (each 10.67 m x 3.35 m), 6 NiCd batteries. Average power output: 3 kW.
ADCS
3-axis stabilized. 24 large steering jets (40 kgf) + 12 small steering jets (1.3 kgf). Gyroscopes for attitude sensing. Motion Control System (MCS) deactivated after Zvezda integration; attitude control now handled by Zvezda and CMGs in US segment.
Transmitter Frequency
Unknown
Map
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Azimuth Elevation Time (Local)
Start Azimuth
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