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MESSENGER Primary Mission Phase, data acquisition and discussion
nprev
post Apr 1 2011, 02:05 AM
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Thought it was time to start a new thread, since MESSENGER has definitely arrived! Reserved for post-commissioning observations.


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Holder of the Tw...
post Apr 5 2011, 05:13 AM
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Prime mission underway.

Update
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Phil Stooke
post Apr 5 2011, 02:53 PM
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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


Attached Image


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Explorer1
post Apr 5 2011, 09:29 PM
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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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djellison
post Apr 5 2011, 09:40 PM
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A bad enough hit could kill any spacecraft, especially in the inner solar system.
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Alan S
post Apr 11 2011, 04:18 AM
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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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Phil Stooke
post Apr 11 2011, 12:02 PM
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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


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Holder of the Tw...
post Apr 26 2011, 10:10 PM
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First laser track made from orbit has been released.

Link

This is on a generic link for science highlights, so likely only to be there a few days.

They caught a radar bright crater on this very first pass.

Update: the link for the report on the laser has been archived here.
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OWW
post Jun 2 2011, 11:25 PM
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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... smile.gif

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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JohnVV
post Jun 2 2011, 11:50 PM
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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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elakdawalla
post Jun 3 2011, 02:48 AM
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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.


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tanjent
post Jun 3 2011, 11:07 AM
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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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JGodbaz
post Jun 3 2011, 11:25 AM
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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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Holder of the Tw...
post Jun 7 2011, 05:47 AM
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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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Paolo
post Jun 7 2011, 05:18 PM
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that looks like a press briefing just before publication in Science the next day...


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