[FOTZeiss] Fw: Mariner 10 Perspective on MESSENGER: A First-person Account

[Glenn A. Walsh]

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gaw

Glenn A. Walsh, Project Director,
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--- On Wed, 6/8/11, Ron Baalke <baalke at ZAGAMI.JPL.NASA.GOV> wrote:

> From: Ron Baalke <baalke at ZAGAMI.JPL.NASA.GOV>
> Subject: A Mariner 10 Perspective on MESSENGER: A First-person Account
> To: HASTRO-L at listserv.wvu.edu
> Date: Wednesday, June 8, 2011, 6:05 PM

> http://messenger.jhuapl.edu/soc/highlights.html
> 
> MESSENGER Science Highlights from Mercury's Orbit
> June 7, 2011
> 
> A Mariner 10 Perspective on MESSENGER: A First-person
> Account
> Robert Strom
> 
> Forty years ago, in 1971, I became a member of the Mariner
> 10 imaging
> science team. This Mercury flyby mission was intended to
> gather
> atmospheric data at Venus and geological and geophysical
> data at Mercury
> in preparation for a Mercury orbiter mission. At that time
> we knew
> almost nothing about the innermost planet, and the Mariner
> 10 flybys
> were intended to help in the selection of an instrument
> payload for an
> orbital mission. The Mariner 10 spacecraft flew by Venus
> once and
> Mercury three times. Because of the configuration of the
> flybys and the
> orbit of Mercury, Mariner 10 imaged the same hemisphere of
> Mercury on
> each of its three flybys, for a total surface coverage of
> only 45%. Much
> of this coverage was taken with the Sun high in the sky, a
> situation
> that makes it difficult to see topography. As a result, we
> could perform
> geological analyses on only about 30% of the surface.
> 
> The technique of sending a spacecraft to orbit Mercury
> using multiple
> planetary flybys was discovered in the mid-1980s. However,
> the
> difficulties and expense of a Mercury orbital mission
> (estimated at ~$1
> billion in 1985 dollars), coupled with a perception that
> Mercury was
> similar to the Moon and therefore of low scientific
> priority, meant that
> no such mission was developed for decades. It was not until
> the Carnegie
> Institution of Washington and the John Hopkins University
> Applied
> Physics Laboratory devised a low-cost Mercury orbiter
> concept that an
> orbital mission was approved, as part of NASA's Discovery
> Program.
> I am very privileged to be the only person on the MESSENGER
> Science Team 
> who also participated in the Mariner 10 mission.
> 
> When MESSENGER went into orbit about Mercury on March 18,
> 2011, I was
> overjoyed. I had waited almost 40 years for that moment.
> When the
> spacecraft sent back its first images on March 29, 2011,
> the date was 37
> years to the day after Mariner 10's historic first flyby.
> What a
> coincidence! Since then I have been overwhelmed by the
> quality of the
> MESSENGER's Mercury Dual Imaging System (MDIS) images
> (e.g., Figures 1 and 2) 
> and the data from the six other instruments on the
> spacecraft, and how much better they are than the Mariner
> 10 data.
> Although the Moon and Mercury are both heavily cratered
> surfaces,
> Mercury's history is very different from that of the Moon,
> and the new
> images are making that extremely clear. The MESSENGER
> mission has
> started a new era in planetary exploration and will finally
> provide
> information that will allow us to better understand this
> strange and
> wonderful planet.
> 
> 
> Figure 1. Comparison of Mariner 10 (left) and MESSENGER
> (right) images
> of the Tolstoj impact basin, approximately 350 km in
> diameter. The level
> of detail visible in the MESSENGER mosaic (~220 m/pixel) is
> much greater
> than that in the Mariner 10 mosaic (~1 km/pixel). MESSENGER
> will image
> more than 90% of Mercury's surface at an average resolution
> of 250
> m/pixel or better, a feat that could never have been
> accomplished by
> Mariner 10. MESSENGER is also taking higher-resolution
> targeted images
> <http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?page=1&gallery_id=2&image_id=506>
> at resolutions of 10-25 m/pixel!
> 
> Figure 2. Comparison of Mariner 10 and MESSENGER images of
> Goethe
> crater (383 km in diameter) in the northern plains of
> Mercury. The
> MESSENGER image labeled /b/ on the right is at 200 m/pixel
> and shows the
> region within box /b/ in the Mariner 10 image on the
> left.  A portion of
> a targeted area (box /c/) imaged by MESSENGER at 12 m/pixel
> is shown in
> the inset labeled /c/. Mariner 10 was not able to obtain
> these types of
> high-resolution images.
>