MESSENGER Primary Mission Phase, data acquisition and discussion |
MESSENGER Primary Mission Phase, data acquisition and discussion |
Apr 1 2011, 02:05 AM
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#1
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Merciless Robot Group: Admin Posts: 8785 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
Thought it was time to start a new thread, since MESSENGER has definitely arrived! Reserved for post-commissioning observations.
-------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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Apr 5 2011, 05:13 AM
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#2
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Member Group: Members Posts: 544 Joined: 17-November 05 From: Oklahoma Member No.: 557 |
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Apr 5 2011, 02:53 PM
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#3
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Solar System Cartographer Group: Members Posts: 10229 Joined: 5-April 05 From: Canada Member No.: 227 |
Astro0's mosaic from the end of the previous thread can be extended with this image:
http://messenger.jhuapl.edu/gallery/scienc...mp;image_id=439 Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PDF: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Apr 5 2011, 09:29 PM
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#4
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Senior Member Group: Members Posts: 2106 Joined: 13-February 10 From: Ontario Member No.: 5221 |
Just saw this:
http://www.pbs.org/newshour/updates/scienc...solarstorm.html Would a direct hit have really ended the mission before it began? Scary if true! |
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Apr 5 2011, 09:40 PM
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#5
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Founder Group: Chairman Posts: 14434 Joined: 8-February 04 Member No.: 1 |
A bad enough hit could kill any spacecraft, especially in the inner solar system.
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Apr 11 2011, 04:18 AM
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#6
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Newbie Group: Members Posts: 3 Joined: 24-December 06 Member No.: 1512 |
I see the probe is making passes over the north pole of the planet. When can we expect data regarding the composition of north pole. I'd really like to know it is has ice there.
Alan |
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Apr 11 2011, 12:02 PM
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#7
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Solar System Cartographer Group: Members Posts: 10229 Joined: 5-April 05 From: Canada Member No.: 227 |
From:
http://www.scribd.com/doc/48850455/Messenger-Fact-Sheet-2001 polar cap volatiles– The gamma-ray and neutron spectrometer will determine if Mercury’s polar caps contain hydrogen in water ice, and the laser altimeter will map the caps’ topography and thickness. The particle and plasma and UV spectrometers will detect effluent from the frozen volatiles, even if the cap is formed of elemental sulfur. Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PDF: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Apr 26 2011, 10:10 PM
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#8
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Member Group: Members Posts: 544 Joined: 17-November 05 From: Oklahoma Member No.: 557 |
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Jun 2 2011, 11:25 PM
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#9
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Member Group: Members Posts: 710 Joined: 28-September 04 Member No.: 99 |
Announcement on the Messenger website:
QUOTE June 16, 2011, 1 pm NASA Science Update: Early Science from Mercury Orbit Hopefully some nice mosaics will be released at the same time... BTW, has anybody noticed, in the narrow angle images released thus far, many have a horrible "blocky" texture? What's up with that? Noise? Compression artefacts? Didn't see that in the flyby images. |
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Jun 2 2011, 11:50 PM
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#10
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Member Group: Members Posts: 890 Joined: 18-November 08 Member No.: 4489 |
QUOTE BTW, has anybody noticed, in the narrow angle images released thus far, many have a horrible "blocky" texture? What's up with that? Noise? Compression artefacts? Didn't see that in the flyby images. looks like someone jpg it before the mapping level1 and 2 in cub export to jpg import level3 export to png ( indexed) you can see the "graph " like lines on a diagonal , same as the mapping [attachment=24479:Screenshot_1.png] |
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Jun 3 2011, 02:48 AM
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#11
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Administrator Group: Admin Posts: 5172 Joined: 4-August 05 From: Pasadena, CA, USA, Earth Member No.: 454 |
The "JPEG" compression artifacts are likely due to the onboard wavelet compression, necessary because of limits of onboard memory and downlink bandwidth (remember that MESSENGER does not have a HGA because its pointing is so tightly constrained by the thermal environment; instead it has a steerable phase-array thingamabob that they call the "MGA"). From http://img.pds.nasa.gov/documentation/MDIS_CDR_RDRSIS.PDF:
QUOTE 2.1.3 MDIS Data Compression
The MESSENGER mission requires compression to meet its imaging objectives within the available downlink. Figure 2-5 summarizes the compression options available to MDIS at the instrument level using the DPU and the spacecraft main processor (MP). At the focal plane, 2×2 binning is available on-chip to reduce the 1024×1024 images to 512×512 format. In the DPU, 12-bit data number (DN) levels can be companded to 8 bits, and data can be compressed losslessly. The strategy for DPU image compression is to acquire all monochrome data in 8-bit mode, and color data in 12-bit mode, and to compress all data losslessly to conserve recorder space. After data are written to the recorder, they can be uncompressed and recompressed by the MP more aggressively using any of several options: additional pixel-binning, subframing, and lossy compression using an integer wavelet transform. The nominal strategy for MP compression is that all data except flyby color imaging will be wavelet compressed, typically 8:1 for monochrome data and to a lower ratio (≤ 4:1) for orbital color data. Color imaging but not monochrome imaging may be further pixel-binned. For the special case of optical navigation images, there is a “jailbar” option that saves selected lines of an image at a fixed interval for optical navigation images of Mercury during flyby approaches. Compression performance was extensively modeled prior to launch. The 12-to-8 bit look-up tables have been designed to preferentially retain information at low, medium, or high 12-bit DN values, for a nominal detector bias or for one that has decreased with time (Figure 2-6). Compression ratios to be used for flight have been based on a study of the magnitude and spatial coherence of compression artifacts using NEAR images. For expected loading of the main processor, simulations have shown that the MP can compress the equivalent of 82 full 1024×1024 images per day (or 330 512×512 images per day). The actual number of images has also been simulated, based on orbital trajectory simulations and the imaging plan described below. The MP image compression capabilities are consistent with the mission-average number of images per day. However, on days when lighting is favorable for global mapping, a peak of ~260 images per day may be expected, requiring on-chip binning of most of the data on peak days. The full implications for average imaging resolution are still being assessed. -------------------- My website - My Patreon - @elakdawalla on Twitter - Please support unmannedspaceflight.com by donating here.
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Jun 3 2011, 11:07 AM
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#12
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Member Group: Members Posts: 214 Joined: 30-December 05 Member No.: 628 |
It looks comparable in quality to what the Surveyor landers sent back as they approached the moon, except I think those contained white framing marks.
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Jun 3 2011, 11:25 AM
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#13
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Newbie Group: Members Posts: 16 Joined: 30-March 08 Member No.: 4078 |
Does anyone have any idea where to find the description of the compression algorithm? Apparently it is in a document called:
MDIS Compression Description, Pat Murphy (Which doesn't appear to be available anywhere on the internet.) |
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Jun 7 2011, 05:47 AM
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#14
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Member Group: Members Posts: 544 Joined: 17-November 05 From: Oklahoma Member No.: 557 |
NASA is going to have a science update June 16th on early results from MESSENGER. It will be at 1pm (presumably Eastern Time). No other details as yet.
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Jun 7 2011, 05:18 PM
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#15
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Senior Member Group: Members Posts: 1729 Joined: 3-August 06 From: 43° 35' 53" N 1° 26' 35" E Member No.: 1004 |
that looks like a press briefing just before publication in Science the next day...
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