Vintage Micro: The Original Standardized Microsatellite

It can be argued that one of the key advances in making miniature satellite technology more readily available to a wider range of potential users has been the development of standardized satellites. One recent example of this is CubeSat which consists of cube-shaped units ten centimeters on a side with a mass of no greater than 1.33 kilograms constructed to a fixed standard. These standard units, built using off-the-shelf components, can also be combined in twos or threes or even larger configurations to meet the needs of the user and then be deployed into orbit by a standardized system riding piggyback as part of the launch of a larger primary payload. Such a standardized satellite design offers students, scientists and even do-it-yourself satellite enthusiasts a ready means of performing experiments in Earth orbit.

As innovative as this concept of a standardized satellite is, its origins actually date back almost 60 years to before the dawn of the Space Age. The first standard satellite was actually developed as part of the American Vanguard program. Based on a proposal from the Naval Research Laboratory (NRL), on September 9, 1955 Project Vanguard was chosen to be America’s first civilian satellite project with the goal of launching an Earth orbiting satellite as part of America’s contribution to the upcoming International Geophysical Year – an international, interdisciplinary investigation of the Earth and its interaction with the space environment running from July 1957 to December 1958 (for more on the origins of the program, see “Vanguard TV-3: America’s First Satellite Launch Attempt“).

The Vanguard Program

Vanguard was designed from the start to be a complete system for space exploration. This is why Vanguard is the only American space program to use the same name for the satellite and its launch vehicle. The first stage of the Vanguard launch vehicle consisted of a lengthened Phase II Viking sounding rocket built by the Martin Company. This new first stage was powered by a General Electric X-405 engine based on the one used in the Army’s Hermes rocket program. The new engine burned kerosene and liquid oxygen to produce 125 kilonewtons of thrust. The second stage, built by Aerojet General, was based on the successful Aerobee sounding rocket and used an AJ-10-series rocket engine that developed 33 kilonewtons of thrust using inhibited white fuming nitric acid and symmetrical dimethyl hydrazine as propellants. The guidance system, which was mounted on the second stage, was developed by Minneapolis Honeywell Company. The third stage consisted of a spin-stabilized, metal-cased solid rocket motor developed by the Grand Central Rocket Company. Vanguard stood 22 meters tall and had a mass of about 10,300 kilograms at liftoff making it one of the smallest satellite launchers ever built.

The successful launch of Vanguard 1 on March 17, 1958. (NASA)

After much debate between scientists and engineers, it was decided to scrap the nose-cone satellite concept that had been originally proposed for the program. The Vanguard satellite would instead be a polished metallic sphere with a diameter of 51 centimeters and a mass of about 11 kilograms – at the low end of today’s definition of a microsatellite (i.e. a satellite with a mass of 10 to 100 kilograms). This configuration was chosen to improve the visibility of the satellite to aid in optical tracking from the ground and simplify calculations of the various forces acting on it. By tracking the orbit of the satellite and its evolution over time, the density of the upper atmosphere along the satellite’s orbit could be determined as well as the shape of the Earth’s geoid.

The standard satellite’s shell originally consisted of a polished aluminum alloy sphere with a thickness of 0.5 millimeters coated with 0.025 millimeters of aluminum oxide. Inside the pressurized standard satellite was a central column attached to the outer shell by a spider framework of tubular metal and insulated from it using Teflon pads. This column contained batteries for a few weeks of operation, a telemetry system and a Minitrack transmitter developed by the Bendix Corporation operating at 108 MHz which used four small aerials mounted along the equator of the satellite. Up to a kilogram of scientific instruments could be carried with sensors mounted on the satellite’s outer shell.  This mass limit severely restricted the types of experiments that could be carried by the satellite given the transistor-based technology available at that time.

A diagram of the Vanguard “standard satellite” as shown in US Patent No. 2,835,548. (USPTO)

In the end, five scientific packages were selected to fly on the Vanguard missions. Package I consisted of a detector to measure solar Lyman-α emissions in the 110 to 130 nm range of the ultraviolet and sensors to perform “environmental studies”. The sensors for these latter studies included thermistors to measure the temperature of the satellite’s shell and interior as well as pressure sensors to determine if micrometeoroids had penetrated the outer shell.  As a backup to the Lyman-α experiment, Package Ia carried detectors to measure solar X-rays in the 0.1 to 0.8 nm range in addition to the environmental sensors. Package II consisted of photocells that would use the spin of the satellite combined with its orbital motion to build up crude images of the Earth’s cloud cover. Package IV used detectors to measure the infrared radiation from the Earth’s surface and atmosphere in an effort to determine our planet’s radiation balance – a key piece of information needed in studying weather and climate.

Package III did not use a standard Vanguard satellite. Instead in consisted of a nonconductive fiberglass sphere with a diameter of 33 centimeters with a magnetometer mounted on a boom on the top of the satellite to make precise measurements of Earth’s magnetic field as well as an additional payload of a 76-centimeter diameter aluminized balloon that was to inflate once in orbit.  Optical tracking of the inflated balloon would allow the density of the upper atmosphere to be more accurately determined.

One other nonstandard satellite included in the Vanguard program was a “minimum satellite” used on early test flights. It was a 16-centimeter aluminum alloy sphere with a mass of just 1.47 kilograms (a nanosatellite by today’s standards) that carried a pair of Minitrack transmitter beacons – one battery-powered and another powered by small banks of solar cells on the satelllite’s exterior (see “Vintage Micro: The Original Nanosatellite“).

The Vanguard Missions

In total, the Vanguard program made 11 attempts to orbit a payload including four that were considered “test flights”. But as was typical for these very early days of rocketry, there were many problems encountered and all but three of these launch attempts ended in failure. The first success for the Vanguard program was the launch of a minimum satellite, Vanguard 1, on March 17, 1958 using TV-4 (Test Vehicle-4). It ended up being the second satellite successfully orbited by the United States and the world’s first nanosatellite (see “Vanguard 1: The Little Satellite That Could“). While its battery-powered beacon ceased operating after 20 days in orbit, the solar-powered beacon continued operating for just over six years. Tracking of the satellite provided data on the density of the upper atmosphere and allowed the shape of Earth’s geoid to be significantly refined. Vanguard remains in orbit to this day as the oldest manmade object in space and is expected to remain there for another 180 years or more.

The first “standard satellite” payload on Vanguard TV-5 being prepared for its unsuccessful launch on April 28, 1958. (NASA)

The second successful launch was Vanguard 2 using SLV-4 (Satellite Launch Vehicle-4) on February 17, 1959.  Vanguard 2 carried experiment Package II – the experiment to measure Earth’s cloud cover and how it changed over time. With NASA officially taking over the Vanguard program from NRL in October 1958, this was their first successful satellite launch after a string of failed lunar probe attempts.

According to the original plan, a clamp holding Vanguard 2 to its solid propellant third stage was to release once in orbit allowing a spring to cleanly separate the two. While this took place more or less as planned, a residual discharge from the free flying third stage rocket motor just after separation resulted in the stage bumping the released satellite. Instead of spinning predictably about a predetermined axis, the minor collision set Vanguard 2 wobbling as it traveled around the Earth. Without a means of determining exactly where its sensors were pointing, the stream of brightness values returned by Vanguard 2 could not be reassembled into coherent images by scientists back on the ground. While certainly a disappointment to the experiment’s designers, the data Vanguard 2 returned during its 27-day active life was still quite useful in the development of future weather satellites (see “Vanguard 2: NASA’s First Successful Satellite Launch“).

Cutaway view of Vanguard 3 which was a significantly modified “standard satellite” that carried a much heavier instrument payload. (NASA)

The final launch of the Vanguard program used modified versions of the Vanguard launch vehicle and the standard satellite. By replacing the original third stage with a new fiberglass-cased X-248 solid rocket motor built by the Allegany Ballistics Laboratory (which today is operated by ATK under contract from the US Navy), the Vanguard launch vehicle’s payload capability was more than doubled. This allowed Vanguard 3 to carry a significantly increased instrument payload that demonstrated the versatility of the standard satellite design. In addition to carrying the full instrument payload of Package Ia and Package III with the magnetometer of the latter mounted at the end of a 26-centimeter tall conical fiberglass extension added to the top of the satellite, it also carried additional micrometeorite detectors and an ionospheric sounder. Among the other improvements were a command receiver and a data recorder that could store measurements made when the satellite was not within range of a tracking station.

Vanguard 3 was successfully launched using the modified SLV-7 on September 18, 1959.  It was the last of the Vanguard series and, with a mass of 23.6 kilograms, it was the heaviest.  Although interference from energetic particles in the recently discovered Van Allen radiation belts saturated the Lyman-α experiment’s detectors, the satellite did return excellent quality magnetometer and other data.  Vanguard 3 continued operations until December 8 when its batteries were finally exhausted.

Although the Vanguard program experienced many more failures than successes, it did leave an important legacy for future space programs including its “standard satellite” design that was later used by NRL in many of its small satellites launched as part of the US Navy’s space program (see “Vintage Micro: The First ELINT Satellites“).

Summary of Vanguard Launches

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Related Reading

“Vanguard TV-3: America’s First Satellite Launch Attempt”, Drew Ex Machina, December 6, 2017 [Post]

“Vanguard 1: The Little Satellite that Could”, Drew Ex Machina, March 17, 2018, [Post]

“Vanguard 2: NASA’s First SUccessful Satellite Launch”, Drew Ex Machina, February 17, 2021 [Post]

“Vintage Micro: The First ELINT Satellites”, Drew Ex Machina, September 30, 2014 [Post]

General References

Constance McLaughlin Green and Milton Lomask, Project Vanguard: The NASA History, Dover Publications, 2009

John P. Hagen, “The Viking and the Vanguard”, in The History of Rocket Technology, edited by Eugene M. Emme, Wayne State University Press, pp. 122-141, 1964

J.D. Hunley, U.S. Space-Launch Vehicle Technology: Viking to Space Shuttle, University Press of Florida, 2008

James A. Van Allen, Scientific Uses of Earth Satellites, University of Michigan Press, 1956