Larry J Paxton GUVI coPI SSUSI PI Why spectrograph mode Spectrograph mode returns the entire spectrum When SSUSI was designed the data rate was set as spare words in the OLD data stream about ID: 408478
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Slide1
Spectrograph Mode Overview
Larry J. Paxton
GUVI co-PI
SSUSI PISlide2
Why spectrograph mode?
Spectrograph mode returns the entire spectrum
When SSUSI was designed the data rate was set as spare words in the OLD data stream – about Flowdown of Requirements is the Same as SSUSI 3816 BITS per secondGUVI was similarly constrained by the TIMED projectCan only return the entire spectrum when the scan mirror is not in motion due to constraints on the spacecraft NOT the instrumentSpectrograph mode gives you insights into the ITM system that are more difficult to achieve in imaging mode in which just “colors” are returned.
Spectrograph Mode Data are Continuously being Taken with GUVISlide3
GUVI Spectrographic Mode Produces a full spectrum of 115 – 180 nm FUV
Airglow
every 3 sec
in a fixed directionSlide4
SSUSI F19 Checkout ImageSlide5
F19 SSUSI - Detector #2 in Spectrograph Mode
Spectrograph mode data were collected using detector #2 and the narrow slit with the scan mirror at nadir.
The spectrograph image on the right displays one orbit of data from May 9. The horizontal axis is wavelength. The vertical axis is time. The bright lines on the left side are the 1216Å and 1304Å emissions.Spectrograph image at right shows no evidence of out of band light contamination Slide6
GUVI is not fixed in local solar time – it moves through all local times.
The spectrograph summary plots provide insight into what is happening
Compare from year to year to see if it is driven by “space physics” or “orbital mechanics”Check image plots to see what is visible in a given sceneConsult a member of the GUVI team to discuss the details of the operation and the instrument capability. Interpreting Spectrograph Mode Requires Some SkillSlide7
Pick an interesting time…Slide8
What is going on in the GUVI data?Slide9
Start at L1B Spectrograph GallerySlide10
Picked the orbit on Feb 19 2014 across North AmericaSlide11
Look at next day – Feb 20 2014Slide12
Feb 21 2014Slide13
Feb 21 2014 – next orbitSlide14
Feb 21 2014 – next orbitSlide15
Quiet time
Storm-time
SAA
O/N2: column density ratio; NO: column density of nitric oxide (100-150 km)
Test Results Using GUVI Spectrograph
D
ataSlide16Slide17
L1B available since change in modeSlide18
Level L1A available back to start of missionSlide19
Spectrograph Mode Status
The spectrographic mode provides increased effective sensitivity of the instrument.
Example data in following slide illustrates data quality.Single wavelength latitudinal plot (OI 135.6)
Dayside and aurora brightest features
Nightside shows equatorial ionospheric arcs and smaller scale irregularities.
The curve labeled
“
1 sigma noise level
”
is intended to convey the magnitude of the 1 standard deviation error estimate.
It is normally so small that if it had been displayed as
“
error bars
”
it would not have been visible.
A value at packet number 0 of 20 means that the statistical error in that data point was 20 counts out of about 1500 – for a signal to noise ration of 1500/20 = 75.Slide20
GUVI Spectrograph mode O(135.6) example single orbit dataSlide21
Example GUVI O/N2 measured in imaging mode prior to scan motor malfunctionSlide22
O/N2 from Spectrograph Mode (fixed mirror) confirm data quality
A period of elevated geomagnetic activity April 4-7, 2008
Observed with GUVI spectrograph mode
O/N2 global structure and evolution observed with GUVI
confirms spectrograph mode O/N2 data quality.
High Latitude depletions cover all longitudesSlide23
Spectrograph mode increases our effective sensitivity enormously
The long along track slit means that the effective integration period is now about 9 seconds for a single pixel that is about 5km long (projected to an altitude of 300km)
If we sum the data into 50 km “superpixels” then we can bin 10 of these pixels into one superpixel.
The effective responsivity is then about 9c/R in each 50 km super pixel.
For an effective scale height of 100km for the ionosphere:
1R corresponds to a peak density of about 5x105 cm
-3
[5x10
11
m
-3
]
1R corresponds to about 5 TEC units
1 TECU corresponds to about 54 nsec or 16 cm delay in the GPS L1 signalSlide24
MeV particle noise
Auroral Oval
Equatorial Arcs
Dayglow
AuroraSlide25Slide26
MeV particle noise
Auroral Oval
Equatorial Arcs
Dayglow
AuroraSlide27
2007 Day 135 Orbit 29424Slide28
2008 day 127 Orbit 34712
2hrs LSTSlide29
2008 day 127 Orbit 34712Slide30
Development is required to realize those capabilities
NO NASA money for this work
We encourage the community to help us develop new products/capabilitiesSpectrograph Mode Data Enable New CapabilitiesSlide31Slide32Slide33Slide34Slide35Slide36Slide37