Conception
One of the key aims of the astronomers who designed the Hubble Space Telescope was to use its high optical resolution to study distant galaxies to a level of detail that was not possible from the ground. Positioned above the atmosphere, Hubble avoids atmospheric airglow allowing it to take more sensitive visible and ultraviolet light images than can be obtained with seeing-limited ground-based telescopes (when good adaptive optics correction at visible wavelengths becomes possible, 10 m ground-based telescopes may become competitive). Although the telescope's mirror suffered from spherical aberration when the telescope was launched in 1990, it could still be used to take images of more distant galaxies than had previously been obtainable. Because light takes billions of years to reach Earth from very distant galaxies, we see them as they were billions of years ago; thus, extending the scope of such research to increasingly distant galaxies allows a better understanding of how they evolve.
After the spherical aberration was corrected during Space Shuttle mission STS-61 in 1993, the improved imaging capabilities of the telescope were used to study increasingly distant and faint galaxies. The Medium Deep Survey (MDS) used the Wide Field and Planetary Camera 2 (WFPC2) to take deep images of random fields while other instruments were being used for scheduled observations. At the same time, other dedicated programs focused on galaxies that were already known through ground-based observation. All of these studies revealed substantial differences between the properties of galaxies today and those that existed several billion years ago.
Up to 10% of the HST's observation time is designated as Director's Discretionary (DD) Time, and is typically awarded to astronomers who wish to study unexpected transient phenomena, such as supernovae. Once Hubble's corrective optics were shown to be performing well, Robert Williams, the then-director of the Space Telescope Science Institute, decided to devote a substantial fraction of his DD time during 1995 to the study of distant galaxies. A special Institute Advisory Committee recommended that the WFPC2 be used to image a "typical" patch of sky at a high galactic latitude, using several optical filters. A working group was set up to develop and implement the project.
Read more about this topic: Hubble Deep Field
Famous quotes containing the word conception:
“Every man is in a state of conflict, owing to his attempt to reconcile himself and his relationship with life to his conception of harmony. This conflict makes his soul a battlefield, where the forces that wish this reconciliation fight those that do not and reject the alternative solutions they offer. Works of art are attempts to fight out this conflict in the imaginative world.”
—Rebecca West (1892–1983)
“Whenever I’m asked why Southern writers particularly have a penchant for writing about freaks, I say it is because we are still able to recognize one. To be able to recognize a freak, you have to have some conception of the whole man, and in the South the general conception of man is still, in the main, theological.”
—Flannery O’Connor (1925–1964)
“As in private life one differentiates between what a man thinks and says of himself and what he really is and does, so in historical struggles one must still more distinguish the language and the imaginary aspirations of parties from their real organism and their real interests, their conception of themselves from their reality.”
—Karl Marx (1818–1883)