LORRI First Light Options

[SigurRosFan]

- Pluto-Bound Camera Sees 'First Light'

M7:


--- On Aug. 29, 2006, the New Horizons Long Range Reconnaissance Imager (LORRI) opened its launch cover door and took its first image in space, of Messier 7, a star cluster in our Milky Way galaxy. The image shows the center of Messier 7, which was catalogued by Charles Messier in 1764, and described by Ptolemy around 130 A.D. Stars to at least 12th magnitude are clearly visible, meaning LORRI's sensitivity and noise levels in space are consistent with its pre-launch calibrations on the ground. Directionally, north is at the top of the images, east is to the left. ---

[stevesliva]

"Before then LORRI will focus on the Jupiter system, taking its first pictures of the giant planet on Sept. 4."

Neat. Let's see it

[tfisher]

Cool, its great to see that LORRI is working well!

Looking more closely at the web images, these are dropped to 8 bits per pixel from the imager's original 12bpp, but in the negative image (here) the contrast is stretched so we can see the shades of black of the background. Stretching it still further, the result shows the camera artifacts:

The vertical lines I understand: since LORRI takes pictures in a pushbroom fashion (TDI, I guess it is called now) the same elements of the CCd sweep down the picture, so the minute differences in sensitivity give rise to streaks down the picture. There is also a some horizontal banding at the bottom which I don't understand: maybe something to do with the start or end of the imaging sequence? I also wonder how hard flat-fielding is going to be to post-process these artifacts away. It looks like the vertical grain isn't completely uniform: individual streaks get darker and lighter in the same column of pixels, so for instance just subtracting the average of each column isn't going to do it.

Anyway, very exciting. I can't wait until we get to Jupiter!

[mcaplinger]

The vertical lines I understand: since LORRI takes pictures in a pushbroom fashion (TDI, I guess it is called now)...

Ralph is TDI, but as far as I know, LORRI is just a framing camera, not a pushbroom. (And BTW, pushbroom and TDI mean different things.) This looks like a small amount of H register readout noise to me, but the noise level seems very low.

[Comga]

Ralph is TDI, but as far as I know, LORRI is just a framing camera, not a pushbroom. (And BTW, pushbroom and TDI mean different things.) This looks like a small amount of H register readout noise to me, but the noise level seems very low.

LORRI *IS* a frame camera. The streaks are more likely due to "hot" pixels and their distribution amongst the columns. That is, a column with more pixels with above average dark current will seem to have a bright streak in it. A column with fewer will seem to be a dark streak. As these bright and dark streaks are there in every frame, a "dark frame" can be recorded, for instance by pointing at a region of the sky with few stars, and removed from the science images in post processing. There are also variations in sensitivity between the individual pixels that can be corrected. That and a few other steps are what it takes to get the nearly flawless images we are used to seeing, like in the publication quality releases from Hubble.

TDI, or time delay integration, is a form of pushbroom scanning where there are parallel registers across the field of view. An "electronic image" of electrons stored in the array is formed in the first row as the optical image sweeps across it. This electronic image is clocked along at the same rate the image is being swept over the detector. As the optical image and electronic image move at the same speed (with the electronic image jumping from row to row) there is more time to build up an image. The MVIC arrays in Ralph so work in this fashion, with 32 rows of 5000 pixels each in each of six arrays. (Two "panchromatic" i.e. full spectrum for "black and white" images and four arrays filtered for color: Red, Blue, Near IR, and a band for detecting Methane.)

[ustrax]

"Before then LORRI will focus on the Jupiter system, taking its first pictures of the giant planet on Sept. 4."

Neat. Let's see it

Any idea on when will this pictures be released?...

[ugordan]

They have to be downlinked first.
Not sure how often the DSN passes are made now and how high a priority the images have for d/l. After that, we wait for a mission update to be written!

[hendric]

Seds page for amateur photos of M7. The middle image is a good comparison to LORRI.

http://www.seds.org/messier/more/m007_m2.html

[tfisher]

LORRI *IS* a frame camera. [...]

D'oh, I stand corrected. Thanks for that explanation.

[Decepticon]

Any images yet?


When does full time observations start with jupiter?

[SigurRosFan]

I mean full time observations lasting from January to June 2007.

[stevesliva]

New update from Alan, and a very candid one at that:
http://pluto.jhuapl.edu/overview/piPerspec...ive_current.php

That said, we have had a few surprises. Ralph's LEISA infrared spectrometer sees a tiny, unexpected solar light leak that is a nuisance at present. This will decline (as the Sun dims with distance) such that by the time we reach Pluto it will be virtually undetectable. So too, we've discovered a design error in the way the PEPSSI instrument is aligned on the spacecraft's upper deck, but the consequence of this is only important at Jupiter, not Pluto. (And we can compensate for the error at Jupiter by adjusting the spacecraft pointing by a few degrees.)

We were also surprised to experience a planned spacecraft turn on Sept. 4 that sliced the Sun briefly across the open telescopes of Ralph and LORRI. The combination of the planned, high spacecraft turn rate and our great distance from the Sun (then already 3.45 astronomical units) didn't result in any damage we can detect in either instrument, but nonetheless this accident could and should have been prevented by command load checking software. To ensure it never happens again, we've added additional check steps to the mission simulation codes run against every command load before it is sent to New Horizons.

[Jeff7]

Hopefully there will be plenty of chances over the coming years to run more tests to ensure a flawless Pluto flyby. We can't risk having something like frequently happens on the MER's - one thing goes wrong, and the whole command sequence is aborted. Do that at Pluto, and by the time you realize that something's wrong, formulate a plan, and transmit the instructions, Pluto's already in the rear view mirror.

[nprev]

Well, according to Alan's update, one of the major objectives of the Jupiter flyby is to exercise all of NH's anticipated command modes in order to find bugs early & have plenty of time to fix them...most sensible.

Getting just a sad view of Pluto in the rear view mirror doesn't seem to be a realistic possibility given the fact that there will be eight years of anomaly resolution time available prior to the encounter... ...frankly, I'm still a LOT more worried about blasting through one of Neptune's Trojan points at 20 km/sec...

[ugordan]

there will be eight years of anomaly resolution time available prior to the encounter

Plus, they're more than likely to run the final Pluto observation sequence as a dress rehearsal several times before the actual flyby, just to see everything is happening as it should.