Vanguard 1, launched on March 17, 1958, marks a significant step in space exploration as the first solar-powered satellite. It is also the oldest human-made object still orbiting Earth. The satellite, with a diameter of about 6.4 inches (16.3 cm), demonstrated the viability of solar energy in space missions. While its primary scientific mission has long since ended, Vanguard 1 remains in orbit, serving as a historical marker of early space endeavors and the evolving technology of the era. Its presence in space continues to remind us of the early stages of human efforts in satellite technology.
Today’s (March 17) story of what happened this day in Science, Technology, Astronomy, and Space Exploration history.
Vanguard 1
Vanguard 1 was a marvel of engineering for its time. Weighing just 1.5 kilograms and measuring 16.5 centimeters in diameter, it featured an aluminum sphere design. It was equipped with solar cells for power and included mercury batteries and various transmitters for communication and tracking.
It was a pioneering U.S. satellite (the second satellite launched by the U.S., after Explorer 1, which was launched on February 1, 1958), notable for its role in testing the capabilities of a three-stage launch vehicle and examining how Earth’s orbital environment impacts satellite systems. It played a key role in gathering geodetic data through orbit analysis. As the second U.S. satellite to reach orbit and the inaugural member of the successful Vanguard series, its distinction also includes being the first satellite to harness solar cell power. Remarkably, Vanguard 1 holds the title of the oldest satellite still in Earth’s orbit.
Spacecraft design and Subsystems
The Vanguard 1 satellite was a lightweight aluminum sphere, weighing 1.46 kg (3.2 lbs) and measuring 16.5 cm (about 6.5 inches) in diameter. Inside this sphere was a cylinder with heat shields that housed the satellite’s instruments, including mercury batteries and two transmitters: a 10-mW, 108-mHz telemetry transmitter, and a 5-mW, 108.03-mHz Minitrack beacon transmitter.
These were powered by six solar cells, each roughly 5 cm (about 2 inches) square, made of single-crystal silicon. The satellite also had six spring-actuated aluminum alloy aerials, each 30 cm (about 11.8 inches) long and 0.8 cm (about 0.31 inches) in diameter, arranged perpendicularly through the sphere’s center. These components were crucial for tracking and data collection. Additionally, Vanguard 1 was equipped with thermistors for monitoring internal temperatures and a unique cylindrical separation mechanism for deployment from its launch vehicle.
Launch
The Vanguard program used the same name for both its satellite and its launch vehicle. The launch vehicle was a three-stage rocket:
- The first stage was powered by a GE X-405 liquid rocket engine, utilizing kerosene and liquid oxygen as fuel, and was notable for its significant thrust and large size. It was finless, 13.4 meters (44 feet) tall, 1.14 meters (45 inches) in diameter, and had a launch mass of approximately 8,090 kg (17,800 lbs). It produced 28,000 pounds (~125,000 N) of thrust.
- The second stage, with an Aerojet-General AJ-10 engine, used a different fuel combination and was equipped with a guidance and control system. It was 5.8 meters (19 feet) high and 0.8 meters (31.5 inches) in diameter. It produced a thrust of 7340 pounds (~32,600 N) and had a launch mass of approximately 1990 kg (4390 lbs).
- The third stage, developed by the Grand Central Rocket Co., used a solid-propellant rocket and was designed to complete the satellite’s deployment into orbit. It was 1.5 meters (60 inches) high, 0.8 meters (31.5 inches) in diameter, and had a launch mass of 194 kg (428 lbs). It produced 2350 pounds (about 10,400 N) of thrust (for 30 seconds burn time).
The total height of the launch vehicle with the satellite fairing was about 21.9 meters (72 feet). The payload capacity was 11.3 kg (25 lbs.) to 555 km (345 miles) Low Earth Orbit (LEO, see notes 1). A nominal launch would have the first stage firing for 144 seconds, bringing the rocket to an altitude of 58 km (36 mi), followed by the second stage burn of 120 seconds to 480 km (300 mi), whereupon the third stage would bring the satellite to orbit.
This configuration was used for various Vanguard missions, with slight modifications for each launch.
Vanguard 1 was launched on March 17, 1958. The three-stage launch vehicle placed the spacecraft into a 654 x 3,969 km (406 x 2,466 miles), 134.27-minute elliptical orbit inclined at 34.25°.
Mission
The initial expectation was that Vanguard 1’s orbit would last around 2000 years. However, factors such as solar radiation pressure and atmospheric drag, particularly during periods of heightened solar activity, caused considerable changes in the satellite’s orbit, specifically in its perigee height. This led to a revised estimate of the satellite’s operational lifespan, reducing it to about 240 years.
The satellite’s battery-powered transmitter ceased functioning in June 1958 as the batteries depleted. Its solar-powered transmitter continued to operate until May 1964, with the final signals received in Quito, Ecuador. Post this period, Vanguard 1 has been monitored through optical tracking from Earth.
Vanguard 1 played a crucial role in measuring the densities of the Earth’s upper atmosphere. Its symmetrical shape allowed scientists to accurately determine atmospheric densities based on various factors like altitude, latitude, season, and solar activity. The satellite’s orbit would slightly deviate from its predicted path due to atmospheric drag, and these deviations were meticulously analyzed.
By studying the rate and pattern of these orbital shifts and considering the satellite’s drag properties, researchers could infer the characteristics of the upper atmosphere. They concluded that atmospheric pressures and drag were higher than initially thought, leading to faster orbital decay.
Vanguard 1 is the Oldest Human-Made Object Still in Orbit
Vanguard 1 remains in orbit today, holding the distinction of being the oldest human-made object still orbiting Earth. Its original mission concluded in 1964, and it, along with the upper stage of its launch rocket, became non-operational but continued to orbit.
As explained above, initially, it was thought that Vanguard 1 might stay in space for up to 2,000 years. However, factors like solar radiation pressure and atmospheric drag have since reduced its expected orbital lifespan to about 240 years, with an anticipated re-entry into the atmosphere in the late 22nd century.
As space travel evolves, there’s a possibility that Vanguard 1 might be retrieved as a significant artifact from the early era of space exploration.
Video: The Oldest Satellite In Space – Vanguard 1
In Scott Manley’s video titled “The Oldest Satellite In Space – Vanguard 1,” he explores the history and significance of Vanguard 1, the fourth satellite ever launched, following Sputnik 1, 2, and Explorer 1. He delves into the challenges it faced, including multiple high-profile launch failures. Despite these setbacks, Vanguard 1 remains notable for its longevity, still orbiting Earth 60 years after its launch, outlasting its predecessors. Manley also highlights how the Vanguard rocket’s design was ahead of its time, aligning more closely with modern launch vehicles.
Notes
- Low Earth Orbit (LEO) refers to an Earth-centered orbit with an altitude between approximately 160 kilometers (99 miles) and 2,000 kilometers (1,200 miles). This orbit is used for many satellites, including those for communications and Earth observation, due to its proximity to the Earth’s surface, which allows for lower launch costs and stronger signal strengths.
Sources
- Vanguard 1 on the NASA Space Science Data Coordinated Archive website
- Vanguard Satellite, 1958 on the NASA website
- Vanguard 1 on Wikipedia
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