The science instruments aboard Hubble are large, complex devices. Some are similar in size and shape to a telephone booth and others are similar to a grand piano. The telescope was designed to hold four telephone booth-sized instruments and four piano-shaped instruments. The latter includes three Fine Guidance Sensors, which can also collect science data. The instruments take electronic pictures of stars and send the picture data to the ground where scientists analyze the information to make discoveries about our universe.

This picture shows an astronaut removing the Goddard High Resolution Spectrograph in preparation for a new instrument during the Second Servicing Mission.
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