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The Hipparcos satellite was solely devoted to astrometry. It did not take 'regular' images, it used an eccentric Schmidt telescope to overlay images onto a grid. It finally resulted in a catalogue of stars, not an archive of images. It's purpose was to detect and find the position of stars in the sky.

An 'image' taken by Hipparcos. As you can see, it's more of a measurement than an image. (Courtesy Wikimedia Commons

The Hubble space telescope was exactly what it says on the box; a telescope. It consisted of five scientific cameras and a Ritchey–Chrétien telescope. It's function is to take advanced images of distant worlds in incredible detail.

Image of the Butterfly Nebula, taken by Hubble. (Courtesy Wikimedia Commons)

As you can see, their functions were completely different. Hipparcos was far more accurate when it came to astrometry, and Hubble could not 'replace' it in that aspect.

## Update

Whilst it is true that even Hubble can perform astrometric measurements, this is not it's main function. Hipparcos was specifically designed to measure the sky, and Hubble was specifically designed to image it. Hubble's FGS system was installed primarily to aim it with high precision, not to perform astrometry.

As such, Hubble's astrometry has a median accuracy of $$±0.0003 arcseconds$$, whilst Hipparcos has a median accuracy of $$±0.0001 arcseconds$$.

The Hipparcos satellite was solely devoted to astrometry. It did not take 'regular' images, it used an eccentric Schmidt telescope to overlay images onto a grid. It finally resulted in a catalogue of stars, not an archive of images. It's purpose was to detect and find the position of stars in the sky.

An 'image' taken by Hipparcos. As you can see, it's more of a measurement than an image. (Courtesy Wikimedia Commons

The Hubble space telescope was exactly what it says on the box; a telescope. It consisted of five scientific cameras and a Ritchey–Chrétien telescope. It's function is to take advanced images of distant worlds in incredible detail.

Image of the Butterfly Nebula, taken by Hubble. (Courtesy Wikimedia Commons)

As you can see, their functions were completely different. Hipparcos was far more accurate when it came to astrometry, and Hubble could not 'replace' it in that aspect.

The Hipparcos satellite was solely devoted to astrometry. It did not take 'regular' images, it used an eccentric Schmidt telescope to overlay images onto a grid. It finally resulted in a catalogue of stars, not an archive of images. It's purpose was to detect and find the position of stars in the sky.

An 'image' taken by Hipparcos. As you can see, it's more of a measurement than an image. (Courtesy Wikimedia Commons

The Hubble space telescope was exactly what it says on the box; a telescope. It consisted of five scientific cameras and a Ritchey–Chrétien telescope. It's function is to take advanced images of distant worlds in incredible detail.

Image of the Butterfly Nebula, taken by Hubble. (Courtesy Wikimedia Commons)

As you can see, their functions were completely different. Hipparcos was far more accurate when it came to astrometry, and Hubble could not 'replace' it in that aspect.

## Update

Whilst it is true that even Hubble can perform astrometric measurements, this is not it's main function. Hipparcos was specifically designed to measure the sky, and Hubble was specifically designed to image it. Hubble's FGS system was installed primarily to aim it with high precision, not to perform astrometry.

As such, Hubble's astrometry has a median accuracy of $$±0.0003 arcseconds$$, whilst Hipparcos has a median accuracy of $$±0.0001 arcseconds$$.

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The Hipparcos satellite was solely devoted to astrometry. It did not take 'regular' images, it used an eccentric Schmidt telescope to overlay images onto a grid. It finally resulted in a catalogue of stars, not an archive of images. It's purpose was to detect and find the position of stars in the sky.

An 'image' taken by Hipparcos. As you can see, it's more of a measurement than an image. (Courtesy Wikimedia Commons

The Hubble space telescope was exactly what it says on the box; a telescope. It consisted of five scientific cameras and a Ritchey–Chrétien telescope. It's function is to take advanced images of distant worlds in incredible detail.

Image of the Butterfly Nebula, taken by Hubble. (Courtesy Wikimedia Commons)

As you can see, their functions were completely different. Hipparcos was far more accurate when it came to astrometry, and Hubble could not 'replace' it in that aspect.