Updated: Aug 3
The Hubble Space Telescope has been a game-changer in the field of astronomy, providing unprecedented insights into the cosmos. To ensure its longevity and enhance its capabilities, a series of servicing missions have been carried out by NASA.
This article dives into the details of these missions and their significance in extending the life of this revolutionary telescope, which provided us invaluable data before ceasing its operations.
A Brief Overview of the Hubble Space Telescope
Launched in 1990, the Hubble Space Telescope has been a groundbreaking instrument for observing the Universe. Orbiting Earth at an altitude of about 340 miles, it has captured stunning images and provided invaluable data for astronomers and scientists worldwide.
An astronaut uses a specially designed ratchet during the four days of spacewalks. The power tool was constructed to withstand the harsh environment of space. (Image Credit: NASA/Hubble)
The Need for Hubble Servicing Missions
Hubble's position in low Earth orbit exposes it to harsh conditions, such as radiation and extreme temperature fluctuations. Additionally, its delicate instruments require regular maintenance and upgrades to keep functioning optimally. To address these challenges, NASA has conducted several Hubble Servicing Missions.
Servicing Mission 1 (SM1) - Restoring Hubble's Vision
After Hubble's launch, it was discovered that its primary mirror had a flaw, causing blurry images. SM1, carried out in 1993, successfully installed the Corrective Optics Space Telescope Axial Replacement (COSTAR) and the Wide Field and Planetary Camera 2 (WFPC2) to rectify this problem.
Servicing Mission 2 (SM2) - Expanding Hubble's Capabilities
In 1997, SM2 was launched to further improve Hubble's performance. Astronauts installed the Space Telescope Imaging Spectrograph (STIS) and the Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) to expand Hubble's imaging and spectroscopic capabilities.
In this image STS-125 mission specialist Mike Massimino participates in the fourth of the mission's spacewalks to repair the Hubble Space Telescope. (Image Credit: NASA/Hubble)
Servicing Mission 3A and 3B - Maintaining Hubble's Health
Due to the complexity of the tasks, SM3 was split into two parts: SM3A in 1999 and SM3B in 2002. These missions focused on replacing aging equipment, such as gyroscopes, batteries, and the Fine Guidance Sensor. They also installed the Advanced Camera for Surveys (ACS), which enhanced Hubble's imaging capabilities.
Servicing Mission 4 (SM4) - A Monumental Effort
Originally scheduled for 2004, SM4 was postponed and then canceled following the Space Shuttle Columbia disaster. However, after the successful recovery of the shuttle program and a reevaluation of SM4's risks, NASA approved the mission. SM4, conducted in 2009, was Hubble's most challenging and intense servicing mission, with numerous tasks completed over five spacewalks.
Installing New Instruments
Astronauts installed two new instruments during SM4: the Wide Field Camera 3 (WFC3) and the Cosmic Origins Spectrograph (COS). These cutting-edge instruments made Hubble 100 times more powerful than at its launch.
Wide Field Camera 3 (WFC3)
WFC3 is capable of observing near-ultraviolet, visible, and near-infrared light, with a much greater resolution and field of view than previous instruments. Astronauts removed the Wide Field and Planetary Camera 2 (WFPC2) to make room for WFC3.
Cosmic Origins Spectrograph (COS)
COS is a spectrograph that exclusively observes ultraviolet light. It breaks light into its component colors, revealing information about the object emitting the light. COS improved Hubble's ultraviolet sensitivity at least ten times and up to 70 times when observing extremely faint objects.
Repairing Existing Instruments
SM4 also saw the unprecedented on-site repair of two instruments: the Advanced Camera for Surveys (ACS) and the Space Telescope Imaging Spectrograph (STIS). Both had stopped working due to electrical issues. Astronauts accessed the interior of the instruments, switched out components, and rerouted power to successfully complete the repairs.
Astronaut Jeffrey Hoffman removes Wide Field and Planetary Camera 1 (WFPC 1) during change-out operations during the first Hubble servicing mission. (Image Credit: NASA/Hubble)
Reinforcing and Reinvigorating Hubble's Systems
One of SM4's goals was to fortify and rejuvenate Hubble's basic spaceflight systems. Astronauts replaced all of Hubble's 18-year-old batteries with new, improved ones. They also installed six new gyroscopes for pointing the telescope and a Fine Guidance Sensor for the pointing system. Protective insulating panels, called New Outer Blanket Layers, were added to key equipment bays, and a Soft Capture Mechanism was installed for future spacecraft attachment.
Hubble's unique position above Earth's atmosphere allowed it to observe ultraviolet wavelengths, which have been only partially explored due to the difficulty of making space-qualified ultraviolet detectors. The combination of WFC3 and COS brought high ultraviolet efficiency to Hubble for the first time, enabling new discoveries and observations.
The Hubble Servicing Missions have been instrumental in extending the lifespan and enhancing the capabilities of this revolutionary telescope. With its upgraded instruments and systems, Hubble continued to provide valuable insights into the Universe for many years and left a lasting legacy through its Treasury Programs.