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Mileta Avramovic
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Exploring Voyager: Components, Challenges, and Communication in Deep Space

·598 words·3 mins
Mileta Avramovic
Author
Mileta Avramovic
Information Technologies student at Faculty of Sciences University of Novi Sad.
Table of Contents

Components and How They Work
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  • Telecommunication System:
    • High-Gain Antenna (HGA): A 3.7-meter parabolic dish that transmits and receives signals in S-band and X-band frequencies.
    • Low-Gain Antenna (LGA): Used for emergency communications.
    • Transmitters and Receivers: Include S-band and X-band traveling wave tube amplifiers (TWTAs) for signal transmission and reception.
  • Flight Data Subsystem (FDS): A critical component that synchronizes scientific instruments, formats telemetry data, and manages data storage on the digital tape recorder (DTR).
  • Scientific Instruments:
    • Magnetometer (MAG): Measures the strength and direction of magnetic fields in space.
    • Plasma Wave Subsystem (PWS): Detects and analyzes plasma waves and radio emissions.
    • Low-Energy Charged Particle Instrument (LECP): Measures the flux of low-energy cosmic rays.
    • Plasma Spectrometer (PLS): Analyzes the density, temperature, and composition of plasma (currently inactive due to power constraints).
    • Cosmic Ray Spectrometer (CRS): Detects high-energy cosmic rays from supernovae and other cosmic events.

Science Instruments

  • Power System: The spacecraft are powered by Radioisotope Thermoelectric Generators (RTGs), which convert the heat from the decay of plutonium-238 into electrical energy. The power output decreases by about 4 watts per year.

Damage and Fix
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On November 14, 2023, Voyager 1 ceased transmitting usable data. The issue was identified in the Flight Data Subsystem (FDS), which is responsible for formatting data from the instruments for transmission to Earth. Engineers attempted to resolve the issue by switching to redundant hardware and requesting different telemetry modes. Further analysis revealed a corrupted memory block in the FDS, specifically a 256-word section containing critical instructions. By manually analyzing and correcting the corrupted memory, engineers restored communication on April 20, 2024.

Signal Strength and Communication
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Voyager’s signal strength is extremely weak by the time it reaches Earth, with a transmitting power of only 20 watts. The Deep Space Network (DSN), operated by NASA, uses large antennas (up to 70 meters in diameter) to detect these faint signals. The DSN consists of three primary facilities located around the world to ensure continuous communication with spacecraft as the Earth rotates:

  • Goldstone Deep Space Communications Complex – Located in California’s Mojave Desert, USA.
  • Madrid Deep Space Communications Complex – Located near Madrid, Spain.
  • Canberra Deep Space Communications Complex – Located near Canberra, Australia.

These facilities are strategically placed approximately 120 degrees apart in longitude, allowing at least one complex to maintain contact with Voyager at any given time.

In some cases, signals from multiple antennas are combined to improve the signal-to-noise ratio, a technique known as arraying. This is particularly useful for weak signals from distant spacecraft like Voyager. The uplink signal from Earth to Voyager is much stronger, typically around 100 kilowatts, ensuring that commands can reach the spacecraft even at interstellar distances.

Programming Language
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The Voyager spacecraft use custom-built computers with a custom assembly language. The code is executed on three primary computers: the Command Computer Subsystem (CCS), the Flight Data Subsystem (FDS), and the Attitude and Articulation Control Subsystem (AACS). A simulator on Earth allows engineers to test and debug the spacecraft’s software.

FDS Code

Cause of the Error
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The exact cause of the memory corruption in the FDS is unknown. It could be due to a hardware failure, such as a degraded memory chip, or a software issue. Given the age of the spacecraft and the harsh conditions of space, hardware degradation is a plausible explanation.

Data Transmission
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All signals transmitted by Voyager include frame headers that identify the spacecraft and the type of data being sent. This allows the DSN to distinguish between signals from different missions and process the data accordingly.

References
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https://www.youtube.com/watch?v=wpA8NBzzy00

DESCANSO Design and Performance Summary Series Article 4: Voyager Telecommunications