Tom Woods
LASP/CU
tom.woods@lasp.colorado.edu
LASP/CU: Frank Eparvier, Don Woodraska, Gary Rottman
HAO/NCAR: Stan Solomon, Ray Roble, Giuliana de Toma
NRL: Judith Lean
SpaceWx: Kent Tobiska
GI/UAF: Scott Bailey
TIMED SEE
SORCE SWG July 2002 - 1
TIMED Mission
♦
TIMED primary science goals are to understand :
• energy transfer into and out of the Mesosphere and Lower
Thermosphere/Ionosphere (MLTI) region of the Earth's atmosphere, and
• basic structure (i.e., pressure, temperature, and winds) of the MLTI region
between 60 and 180 km
♦
♦
TIMED launched on Dec. 7, 2001
Normal operations began
on Jan. 22, 2002
Thermosphere
Ionosphere
Mesosphere
Energetics
Dynamics
TIMED SEE
SORCE SWG July 2002 - 2
TIMED Instruments Overview
♦
All instruments measure atmospheric composition, density, and
temperature (even SEE using solar occultations)
♦
SABER
• Cooling-IR
♦
TIDI
• Winds-Visible
♦
GUVI
• Aurora-FUV
♦
SEE
• Solar-EUV
TIMED SEE
SORCE SWG July 2002 - 3
Before TIMED
♦
Some previous missions have also studied the MLTI region:
• Atmospheric Explorer (AE-C, AE-E)
- 1973-1981: composition, winds, plasma, solar EUV
• Solar Mesospheric Explorer (SME)
- 1981-1989: composition, solar UV
• Upper Atmosphere Research Satellite (UARS)
- 1991-present: composition, winds, solar UV, plasma
• Student Nitric Oxide Explorer (SNOE)
- 1998-present: NO, aurora, solar XUV
♦
TIMED improvements include:
•
•
•
•
•
•
♦
Measurement of IR cooling by SABER
Measurement of CO 2 by SABER
Four telescopes for measuring winds by TIDI
GUVI has 25 km spatial resolution for aurora dynamics
Better spectral resolution and coverage for solar EUV irradiance by SEE
Use of improved technology / calibrations by all instruments
AIM SMEX is future explorer that will focus on PMCs
TIMED SEE
SORCE SWG July 2002 - 4
Solar EUV Experiment (SEE) Science Objectives
♦
Study the solar radiation input to the
mesosphere, lower thermosphere, and
ionosphere (MLTI)
•
•
Accurately determine the solar vacuum
ultraviolet (VUV: below 200 nm) irradiance
Study the impact of solar changes on Earth’s
upper atmosphere utilizing atmospheric models
Photochemistry
Examples
Heating
Atmospheric
Layers
Creation of Ionosphere
+
O
→ O + e
ν
EUV
−
XUV
Ozone Creation
O2 
→ O → O 3
ν
FUV
Thermosphere
EUV-FUV
90
Mesosphere
O2
Ozone Destruction
O3 
→ O 2 + O
ν
MUV
Solar
Input
FUV
50
Stratosphere
20
km
Troposphere
200
MUV
NUV-Vis-IR
1000 °K
250
Temperature
PLUS
other effects on
Climate
Surface
Oceans
Temperature
(°K)
QuickTime™ and a
Photo - JPEG decompressor
are needed to see this picture.
Corona
SOHO
EIT He II 30.4 nm
500,000
15,000
Transition Region
Chromosphere
6,000
Photosphere
4,000
♦
Improve the understanding of solar VUV
variability
-
XUV
EUV
Identify and quantify the sources of solar VUV
variability
Develop better models of the solar VUV irradiance
FUV
TIMED SEE
SORCE SWG July 2002 - 5
EGS Measures the Solar EUV-FUV
♦
EUV Grating Spectrograph (EGS)
• Normal Incidence, 1/4 m Rowland
Circle Spectrograph
- 26-195 nm range
− ∆λ = 0.4 nm
- (0.167 nm/pixel)
EUV
FUV
Example EGS
Measurement
• Redundant channel used weekly for
tracking degradation
Lyman-α Filter
Calibration accuracy < 10%
Measurement precision < 2%
Charge
Amp
64 x 1024
CODACON
Detector
Flat Field
(Hg) Lamp
Vacuum
Door
Detector
HVPS
Slit
Selector
TIMED SEE
Optical Cube
Solar Aspect Sensor
(SAS)
SORCE SWG July 2002 - 6
XPS Measures the Solar XUV
Calibration accuracy < 20%
Measurement precision < 1%
♦
XUV Photometer System (XPS)
• 8 XUV Si photodiodes
- 0.1-27 nm
− ∆λ ~ 7 nm
Example XPS Measurement
• 1 Lyman-α (121.6 nm) photometer
• 3 bare (Vis) Si photodiodes
- measure FS filter transmission
• 8 position filter wheel
- 1 clear aperture per diode
- 2 fused silica filters per diode
- 5 blank apertures per diode
12 PhotoDiode
Detectors
Amplifiers
&
VFCs
Interface
Board
Filter Wheel
Mechanism
Filter Wheel
Control
Electronics
LVPS
XPS - Generic
Channel Interface
Filter
Wheel
(inside
purge
cover)
Photodiode
Electronics
Section
+28V
XPS
To
MU
Solar
Radiation
Filter
Wheel
Control
Electronics
TIMED SEE
SORCE SWG July 2002 - 7
SEE is Healthy and Working Well
♦
Obtain ~100 solar measurements per week
• Each solar measurement is ~20 10-second
integrations
• A solar observation is performed each orbit
♦
Perform ~3 EGS detector flatfield
calibrations per week
SEE has been in
normal operations
(daily measurements)
since Jan. 22, 2002
• On-board Hg lamp is flatfield source
♦
♦
♦
Make redundant channel (calibration) solar
observation once a week for tracking
degradation
Occultation experiments are possible for
about 2 weeks per yaw around period
Plan an underflight rocket calibration once
a year
12 hr Example for
SEE Observations
Detector Flatfields
Solar Observations
• First calibration rocket was launched on
Feb. 8, 2002
TIMED SEE
SORCE SWG July 2002 - 8
Status of SEE Data Processing
♦
SEE data products are being generated daily
• Version 4 is current version
♦
SEE XPS Level 2 data products are available now
• SEE data and S/W: http://lasp.colorado.edu/see/
- daily average, instrument resolution (~7 nm), atmospheric absorption
corrected, degradation corrected, normalized to 1 AU
- NetCDF format: use IDL read_netcdf.pro to read SEE data products
- Quick-look: use IDL plotxps_ts.pro to plot time series for 1 channel
♦
SEE EGS data products should be available in late July
- EGS re-processing (version 5) includes underflight rocket calibration
results, in-flight FOV and 2nd order maps, and flatfield lamp degradation
- EGS irradiance results shown today are mostly version 4 data, which
don’t have the latest calibrations incorporated yet
TIMED SEE
SORCE SWG July 2002 - 9
XPS Validations with SNOE: 2-7 nm
2-7 nm
SNOE
Rocket
SNOE 2-7 nm irradiances are
higher than SEE 2-7 nm
values by ~30%.
SEE
However, earlier SNOE 2-7
nm measurements, as
compared to F10.7, are more
consistent with SEE.
TIMED SEE
SORCE SWG July 2002 - 10
XPS Validations with SNOE: 17-20 nm
17-20 nm
SNOE
Rocket
SNOE 17-20 nm irradiances
agree very well with the SEE
17-20 nm values.
SEE
SEE confirms the important SNOE
result that the solar XUV irradiance
below 20 nm is about 4 times more
than the historical values
[Hinteregger et al., 1981].
TIMED SEE
SORCE SWG July 2002 - 11
Atmosphere Confirms Higher XUV Irradiances
Modeling of TIMED GUVI Dayglow [Stan Solomon, Spring AGU 2002]
Model with
Reference XUV
Model with
SEE XUV
TIMED GUVI
Measurement
Daily average, near equator, SZA ~ 50°, F10.7=257
TIMED SEE
SORCE SWG July 2002 - 12
EGS Validation with UARS: 120-195 nm
♦
Initial comparison showed
differences of ~30%
EGS Version 4
• ~20% was systematic offset - thought
to be due to pre-launch degradation of
SEE EGS
• ~10% was reduced by including new
calibration parameters (FOV, degradation)
♦
SEE EGS Version 5 has minor
differences between SOLSTICE
• Feb. 2002 rocket calibration confirms
the UARS SOLSTICE irradiance
levels
• EGS Version 5 data include the latest
parameters for FOV, 2nd Order, and
rocket/SOLSTICE calibration
TIMED SEE
EGS Version 5
EGS Version 4
SORCE SWG July 2002 - 13
TIMED-SORCE Validation Plans
♦
SORCE XPS
• 0-35 nm overlap between SORCE XPS and SEE XPS/EGS
♦
SORCE SOLSTICE - FUV (G channel)
• 115-195 nm overlap between SOLSTICE and EGS
♦
♦
♦
Weekly redundant channel measurements by both
SORCE and SEE instruments
Annual rocket calibration experiments for SEE
Important solar Lyman-α irradiance will be well
measured by SORCE and SEE
• 6 different measurements: SEE XPS, SEE EGS x 2, SORCE
XPS, SORCE SOLSTICE x 2
• 3 different measurements from annual rocket experiment
TIMED SEE
SORCE SWG July 2002 - 14
TIMED Fills the “EUV Hole”
Satellite Measurements of the Daily Solar Spectral Irradiance
SORCE
SBUV
NPOES
UARS
SME
SOLRAD
EUV Hole
SOHO
GOES XRS
TIMED SEE
SDO
GOES
AE
TIMED
AEROS
Future FUV
Hole ?
SNOE
SORCE SWG July 2002 - 15
TIMED Mission Began at Solar Maximum
♦
♦
TIMED was just in time for solar maximum
Solar cycle 23 may already be dropping towards solar
minimum conditions
“EUV Hole” Has Been Filled
Prior to the SOHO measurements, the
solar EUV/XUV irradiances had not
been measured on a daily basis since
1980 by the AE-E satellite. Dick
Donnelly had dubbed this problem as
the “EUV Hole”. The TIMED SEE
instrument is the first instrument to
measure the solar irradiance over the
full EUV spectral range (0-120 nm) on
a daily basis and thus ending the EUV
Hole.
SOHO
EIT
He II 30.4 nm
Solar Min
Max
XUV During
Solar Cycle
23
TIMED SEE
SORCE SWG July 2002 - 16
SEE Measures Solar Variability
XPS
Time Series
Version 4 Data
XPS data include
lots of X-ray flares
EGS
Time Series
Current V4 EGS
data still require
several calibration
corrections
Updated FOV Maps
Degradation Correction
Rocket Calibration Update
These corrections have been updated for the XPS Version 4 data, but these
corrections, being more complicated for EGS, will be included in EGS Version 5.
TIMED SEE
SORCE SWG July 2002 - 17
Special Study is Large Flare on April 21
TRACE
1 hour
later
• X1.5 class flare at ~2 UT
• C8 class flare at ~18 UT
LOG Scale
SOHO EIT
X-rays and coronal lines
show most variation
• X-ray increased by factor of 8
• Longer wavelengths enhanced
much less (< 40%)
TIMED SEE
SORCE SWG July 2002 - 18
Solar Rotation (27-day) Variations
♦
♦
♦
Fairly strong 27-day variation seen in late April
EGS degradation is not included yet as evident for the brighter lines in EGS
Trend is similar to “reference” variation but significant differences, such as for
H continuum (80-90 nm) and XUV (< 30 nm), need to be studied in more detail
at other time periods
Pre-TIMED reference 27-day
variation that is based on UARS,
SNOE, rockets, and AE-E results
[Woods and Rottman, in
Comparative Aeronomy, 2002]
XPS
EGS
TIMED SEE
SORCE SWG July 2002 - 19
SEE’s Occultation Will Yield O, O 2, and N2 Densities
Normal Solar
Occultation
SEE occultation experiments are
possible about 2 weeks per yaw
around period
Unit Optical Depth for Solar Min. Condition
Raw SEE data is used for this example
(no corrections for dark, scattered light, etc.)
TIMED SEE
SORCE SWG July 2002 - 20
SEE Team’s Future Science Effort
♦
Validating the absolute solar irradiance values
• Comparisons with SOHO, SNOE, and UARS measurements
• Comparisons with SORCE XPS and SOLSTICE measurements
♦
♦
Characterizing the solar UV variations as function of
wavelength and over different time scales
Modeling the atmospheric response to the measured solar
variations
• Photoelectron response studies using FAST photoelectron data and the ‘glow’
model (Stan Solomon, Scott Bailey, Frank Eparvier)
• Atmospheric response studies using TIME-GCM (Ray Roble, Stan Solomon)
♦
Modeling the solar variation
• Study active feature evolution using SOHO, TRACE, and PSPT images
(Judith Lean, Tom Woods, Giuliana de Toma, Dick White)
• Improve models of the solar irradiance (NRLEUV: Judith Lean,
SOLAR2000: Kent Tobiska, SunRise: Dick White, Peter Fox)
TIMED SEE
SORCE SWG July 2002 - 21