Tau Chart, Comparing both rovers |
Tau Chart, Comparing both rovers |
Jun 30 2006, 03:10 PM
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#1
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Founder Group: Chairman Posts: 14433 Joined: 8-February 04 Member No.: 1 |
I visited this data early on, but there's 600+ sols worth now, so I've revisited it
I thought it would be interesting to comapre Tau values form both rovers at the same time - so to that end I added 21 to the sol number of each Opportunity tau observation to bring it in to line, within a sol, of Spirit observations. What does it show? (remember to subtract 21 to get ACTUAL Opportunity Sol numbers) Well - both rovers experience a large increase from around Sol 350-370, but for Opportunity it peaked briefly significantly higher. Spirit experienced two local events, 380 and 420, Opportunity a long, small peak around 450 and another, shorter one at 480, and the share the big spike at 510ish. Interesting stuff anyway - when you match them up, time wise ( i.e. +21 on MERB sol numbers ) they match quite closely. Doug
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Jun 30 2006, 03:17 PM
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#2
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Member Group: Members Posts: 311 Joined: 31-August 05 From: Florida & Texas, USA Member No.: 482 |
I visited this data early on, but there's 600+ sols worth now, so I've revisited it I thought it would be interesting to comapre Tau values form both rovers at the same time - so to that end I added 21 to the sol number of each Opportunity tau observation to bring it in to line, within a sol, of Spirit observations. What does it show? (remember to subtract 21 to get ACTUAL Opportunity Sol numbers) Well - both rovers experience a large increase from around Sol 350-370, but for Opportunity it peaked briefly significantly higher. Spirit experienced two local events, 380 and 420, Opportunity a long, small peak around 450 and another, shorter one at 480, and the share the big spike at 510ish. Interesting stuff anyway - when you match them up, time wise ( i.e. +21 on MERB sol numbers ) they match quite closely. Doug Nice chart: weird how Tau always increases as a huge spike that then levels off. I guess dust only is replenished back up into the high levels of the atmosphere during storm-like events, so a sudden burst of dust hits a site all at once and then tapers off slowly as the dust settles out? Do we have about another 100 Sols before the next storm season begins? |
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Jun 30 2006, 07:57 PM
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#3
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Rover Driver Group: Members Posts: 1015 Joined: 4-March 04 Member No.: 47 |
sorry for my ignorance- tau=optical depth?
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Jun 30 2006, 08:19 PM
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#4
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Founder Group: Chairman Posts: 14433 Joined: 8-February 04 Member No.: 1 |
I'm not sure of the actual units, but a high number is murkier, dustier air.
Doug |
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Jun 30 2006, 08:45 PM
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#5
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Senior Member Group: Members Posts: 1636 Joined: 9-May 05 From: Lima, Peru Member No.: 385 |
The Tau chart would be much nice if the x-axis is labeled as Summer, Winter, Fall or Spring Southern Hemisphere so that I can correlate better the periodicity of Tau among the sessons: Winter: Low Tau (clear time with index lower than 1.0) and Summer: High Tau (if the index is above than 3.0, the sky is murky due to the increased winds and DD).
Rodolfo |
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Jun 30 2006, 11:39 PM
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#6
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Dublin Correspondent Group: Admin Posts: 1799 Joined: 28-March 05 From: Celbridge, Ireland Member No.: 220 |
sorry for my ignorance- tau=optical depth? Yep Tau is optical depth. Direct insolation is e(-tau)*top of atmosphere insolation. Indirect insolation is a whole other ball of wax. Generally correlates to some degree with atmospheric dust levels on mars. AFAIK it's dimensionless, like a coefficient of friction or drag. |
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Jul 15 2006, 05:27 PM
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#7
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Junior Member Group: Members Posts: 50 Joined: 16-January 06 Member No.: 646 |
The Tau chart would be much nice if the x-axis is labeled as Summer, Winter, Fall or Spring Southern Hemisphere so that I can correlate better the periodicity of Tau among the sessons: Winter: Low Tau (clear time with index lower than 1.0) and Summer: High Tau (if the index is above than 3.0, the sky is murky due to the increased winds and DD). "low tau" would be more like < 0.2-0.3. the "high tau" values mentioned would most likely be associated with a large dust storm. however, tau > 1 is typically considered "high"...for dust. water ice clouds would be another story. |
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Jul 15 2006, 05:28 PM
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#8
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Junior Member Group: Members Posts: 50 Joined: 16-January 06 Member No.: 646 |
Yep Tau is optical depth. Direct insolation is e(-tau)*top of atmosphere insolation. Indirect insolation is a whole other ball of wax. Generally correlates to some degree with atmospheric dust levels on mars. AFAIK it's dimensionless, like a coefficient of friction or drag. tau is dimensionless. |
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