[X] My Assistant

[edstrick]

"Too Cheap" can compromize you till you fail to achieve the primary mission goals. I'm afraid, despite the spectacular degree of the NEAR Eros orbiter mission's success, including it's "obviously impossible" landing on the asteroid, many scientists feel the mission failed to achieve it's primary mission objective: Proving that S Type Asteroids are or are-not the parent bodies of chondritic meteorites.

The camera was small, with frame dimensions since Mariner 4, with non-square pixels, and a good deal of perioduc and random noise clearly visible in 8-bit versions of the images. After the attutude upsed during the "anomaly" at the initial rendezvous burn at Eros, the camera also had some significant fogging due to vented hydrazine or combustion product contamination, that didn't help, either.

The infrared spectrometer failed relatively early in the orbital period and wasn't able to clearly separate fresh and non-fresh exposures of surface material, and the X-ray and Gamma ray instruments simply weren't sensative enough and didn't have enough dwell-time and spatial resolution to resolve fresh from non-fresh material from very low orbital passes. In fact, the only really good gamma data for some analysis from the mission was the data taken after landing.

The mission was a major success, but still, it just didn't really do the job it was supposed to be able to do for the mission to be fully justified.

[Guest_BruceMoomaw_*]

Jeffrey Bell (the one at the U. of Hawaii) certainly thinks NEAR fizzled at that task. Indeed he thinks that nothing short of an asteroid sample return can setttle the issue; he takes a dim view of remote compositional observations in general.

As for Discovery: NASA has now announced that the cost cap for the next Discovery selection has been hiked all the way up to $450 million -- which also means that there are going to be fewer missions. The plan was to release the new Announcement of Opportunity this week -- but there has been a delay: apparently someone has now managed to persuade Congress to launch an investigation of the whole Discovery program, with as-yet uncertain ultimate consequences.

[Guest_Sunspot_*]

http://www.eso.org/outreach/press-rel/pr-2005/pr-15-05.html

Preparing for the Impact
ESO Telescopes Take Snapshot of Comet 9P/Tempel 1 in Readiness for Major Observation Campaign

[Guest_Sunspot_*]

http://www.floridatoday.com/apps/pbcs.dll/.../505310327/1006

CAPE CANAVERAL - Deep Impact is on track to smash its impactor into a comet July 4, but its high-resolution camera's focus is still imperfect.

[Guest_Sunspot_*]

Jun. 9 -- Deep Impact Briefing - NASA TV

10 a.m. PDT

[maycm]

New report on the HRI

http://www.space.com/missionlaunches/05060...act_camera.html

[Bob Shaw]

It appears that Deep Impact is suffering from a re-run of the old Hubble optical problem. Ball Aerospace used an optical surface during the camera manufacturing process which changed shape slightly with different temperatures, and the flyby images will need to be deconvoluted to recover detail. The impact vehicle appears to be OK, however.

I think the only response possible is 'D'oh!'.

[dilo]

Tempel-1 pictured with Medium Resolution Imager (MRI) camera:
http://deepimpact.umd.edu/gallery/DI_T1_doy164.html
(quite strange linear artifacts near the comet... ).

A sad question/consideration. The impactor uses a high-precision star tracker, which imply some kind of optical instrument... why they didn't planned to use it (or add a dedicated small camera) to take a "movie" of nucleus approach?
Even using a low resolution and limiting bit rate (let's say, one picture/min) last images should easily reach sub-meter resolution of pre-impact area, a result impossible even with perfectly focused HRI...

[jamescanvin]

A sad question/consideration. The impactor uses a high-precision star tracker, which imply some kind of optical instrument... why they didn't planned to use it (or add a dedicated small camera) to take a "movie" of nucleus approach?
Even using a low resolution and limiting bit rate (let's say, one picture/min) last images should easily reach sub-meter resolution of pre-impact area, a result impossible even with perfectly focused HRI...

It will.

From the Press Kit:

The impactor begins science imaging 22 hours before impact with a pair of full-frame
images -- one exposed for the nucleus, and one exposed for the coma, the dimmer
cloud that surrounds the nucleus. Similar image pairs will then be obtained every two
hours until 12 hours before impact. At that time, the impactor will spend two minutes
taking the same pictures and other data that it will collect during the final two minutes
before impact. This demonstration is designed to verify that it will execute this critical
data-taking correctly during the final and most critical segment of its mission.
Beginning 10 hours before impact, images will be taken every two hours until 8 hours
before impact; every hour from 7 to 4 hours before impact; and every 30 minutes from
3 to 1 hour before impact. At that time, the pace of imaging will increase until it reaches
a maximum of one picture every 0.7 second at about 12 seconds before impact.
Engineers say that odds are at least 50-50 that dust hitting the impactor will end transmission
of its images during the final 10 seconds before impact. The final potential
image that could be transmitted in its entirety is one scheduled at about 2 seconds
before impact, with a scale of about 20 centimeters (approximately 8 inches) per pixel.

[dilo]

Thanks James, I completely missed it (hope this will not happens to impactor camera! ).

[Comga]

To be precise, the neucleus and coma images will be taken with the Impactor Target Sensor, which peers out forward through a port in the Impactor's copper mass. The star tracker points at right angles to this camera. It has a wider field of view with fewer pixels so that it can determine the orientation of the spacecraft relative to the stars.

The number and size of the images returned to the Fly-by spacecraft is constrained by the limited power available for the S-band communications link and the distance between the spacecraft, which grows to >8000 km at impact. Pictures of the surface would be great, but the science is in the impact, which takes priority.

Impact minus 12 days!

[dilo]

Tank you very much, comga!
I understand that impact is the main objective, but can you kindly give a little bit infos about the Impactor Target Sensor (optics/sensor)...?

[Decepticon]

When will science observation start?

[alan]

Deep impact detects comet nucleus
http://www.newsdesk.umd.edu/scitech/releas...?ArticleID=1087

[Comga]

I understand that impact is the main objective, but can you kindly give a little bit infos about the Impactor Target Sensor (optics/sensor)...?

Try
http://deepimpact.umd.edu/tech/instruments.html

which includes the statement

"The MRI telescope is a Cassegrain design with a 12 cm aperture and a 2.1 m focal length. The optics, mounts, and baffle tube are of similar construction to the HRI telescope. The MRI and the Impactor Targeting Sensor are identical other than the filter wheel."

The CCD arrays are the same on all three instruments. They are all on-axis Cassegrain telescopes, with the focal length of the HRI being five times that of the MRI and ITS.