LYRA COSPAR

1
LYRA the
Large Yield Radiometer onboard the ESA PROBA-2
http//LYRA-SWAP.oma.be/
Véronique Delouille1, J.-F. Hochedez1, P.
Fryzlewicz11, A. Ben Moussa1, M. Dominique1, A.
Theissen1 EGU Meeting, Vienna, 24-25 April 2005
CONSORTIUM J.-F. Hochedez1, W. Schmutz2,
M. Nesladek3ab, Y. Stockman4, U. Schühle5,
A. Ben Moussa1, S. Koller2, K. Haenen3b, J.-P
Halain4, D. Berghmans1, J.-M. Defise4,
D. Gillotay6, V. Slemzin7, A. Mitrofanov7, D.
McMullin8, M. Kretzschmar9, M. Dominique1, A.
Theissen1, B. Nicula1, L. Wauters1, S. Gissot1,
V. Delouille1, J.H. Lecat4, H. Roth2,
E. Rozanov2, I. Ruedi2, C. Wehrli2,
R. Van der Linden1, A. Zhukov1, F. Clette1,
M. dOlieslaeger3ab, J. Roggen10, P. Rochus4 1
Royal Observatory of Belgium, Circular Avenue 3.,
B-1180 Brussels, Belgium 2 Physikalisch-Meteorolog
isches Observatorium Davos (PMOD) and World
Radiation Center (WRC), Dorfstrasse 33, 7260
Davos Dorf, Switzerland 3a IMOMEC,
Wetenschapspark 1, B-3590 Diepenbeek, Belgium 3b
Institute for Materials Research, Limburgs
Universitair Centrum, Wetenschapspark 1, B-3590
Diepenbeek, Belgium 4 Centre Spatial de Liège -
Av. Pré Aily B-4031 Angleur - Belgium 5
Max-Planck-Institut für Sonnensystemforschung MPS
- D-37191 Katlenburg-Lindau - Germany 6 Belgian
Institute for Space Aeronomy, Circular Avenue 3.,
B-1180 Brussels, Belgium 7 Lebedev Physical
Institute, 53 Leninsky Prospect, Moscow, 119991,
Russia 8 Naval Research Laboratory, 4555
Overlook Ave., S.W., Washington, DC 20375, USA 9
Istituto Fisica dello Spazio Interplanetario,
Consiglio Nazionale delle Ricerche, Via del Fosso
del Cavaliere, 100, I-00133 Roma, Italy 10
IMEC, Kapeldreef 75, B-3001 Leuven, Belgium 11
Imperial College, London, UK
ABSTRACT LYRA is the solar UV radiometer that
will embark in 2006 on-board PROBA-2, a
technologically oriented ESA micro-mission. LYRA
is designed and manufactured by a
Belgian-Swiss-German consortium (ROB, PMOD/WRC,
IMOMEC, CSL, MPS BISA). LYRA will monitor the
solar irradiance in four carefully selected UV
passbands. The channels have been chosen for
their relevance to Solar Physics, Aeronomy, and
Space Weather 1/ Lyman-alpha (121.6 nm), 2/ the
200-220 nm Herzberg continuum range (interference
filters for the two previous passbands), 3/
Aluminium filter EUV channel (17-70 nm) covering
He II at 30.4 nm, 4/ Zirconium filter XUV
channel (1-20 nm), where solar variability is
highest. The radiometric calibration will be
traceable to synchrotron source standards (PTB
NIST), and the stability will be monitored by
on-board calibration sources (VIS UV LEDs).
LYRA benefits from a new technology of
detectors based on diamond. Diamond sensors make
the instruments radiation hard and solarblind
with such detectors, the filters used to block
the unwanted visible light, and that attenuate
the desired UV radiation, are unnecessary. With
diamond detectors, the accuracy, the cadence, or
an optimal combination of both is improved.
LYRA will be an innovative solar monitoring
tool for operational space weather nowcasting and
research. SWAP (Sun Watcher using APS and image
Processing), a solar EUV imaging telescope, will
operate on PROBA-2 as well. LYRA demonstrates
technologies important for future ESA missions
such as e.g. Solar Orbiter. The sensor devices
are promising for other applications as well
Earth remote sensing, ozone hole monitoring, EUV
lithography, among others.
The SPACECRAFT
LYRA, UV RADIOMETER

• Mission duration 2 Years, launch in 2006
• Orbit dawn-dust sun synchronous orbit
• Dimensions 60 cm x 70 cm x 85 cm, 120 kg
• Payload Technological demonstrators LYRA and
  SWAP

Image courtesy Verhaert
IN-FLIGHT CALIBRATION LAMPS UV LEDs
DEVELOPMENT
SOLARBLIND DIAMOND DETECTORS

• Material Aluminum alloy 6082 T6
• Surface finish Black anodized
• Envelope X 315.0 mm Y 92.5 mm Z
  222.0 mm
• Mass 5.0 kg

Ti/Pt/Au contacts diamond MSM structures
diamond PiN sensor
Images courtesy IMOMEC
For the very first time in a space instrument,
LYRA is using sensors based on diamond, a wide
bandgap material. The LYRA solarblind diamond
detectors are designed and fabricated at IMOMEC,
Belgium with the collaboration of the National
Institute for Materials Science (NIMS), Japan.
The single pixel devices are MSM structures and
PiN junctions, depending on the LYRA channel. The
collaboration between ROB and IMOMEC originates
with the BOLD program (http//bold.oma.be)
submitted to ESA. LYRA contributes to
demonstrating the feasibility of a technology
that will be highly beneficial in the context of
the Solar Orbiter ESA mission.
Each of the 3 units comprises 4 channels. Each
channel corresponds to a collimator and a
detector head (one detector, one filter, two
calibration LEDs and a precision aperture). The
design of the heads takes into account field of
view (opening angles), cleanliness, vibration,
and thermal issues. The LYRA optical design by
PMOD/WRC stems from the photometers of VIRGO
onboard SoHO.
CALIBRATION RADIOMETRIC MODEL
Images courtesy PMOD WRC
CHANNEL DEFINITION FILTERS STATUS
LYRA filter mount

• 4 channels Herzberg (200-220nm), Ly-alpha, Al
  Zr baselined FM filters available
• Lyman-alpha channel is weak in anticipated signal

CSL
OPERATIONS
Dawn-dusk sun-synchronous orbit
The first table shows the expected currents in
the various channels and the second, the ratio of
solar minimum and solar maximum signal in the
four LYRA passbands, calculated from measured
transmittances and responsivities, using solar
spectra (plotted as grey shades in the left
figure). LYRA measurements will be sensitive to
solar activity. A detailed interpretation of LYRA
measurements will be achieved after further data
simulations with various solar spectra, and after
comparison of LYRA data with data of other
instruments.

• The dawn-dusk sun-synchronous orbit is ideal for
  Sun observation, which will occur most of the
  time.
• Regularly, the Si unit and the Redundant Diamond
  unit will be used simultaneously with the nominal
  one to check the diamond performances and aging
  effects. For the same reason, it will also be
  possible to calibrate the detectors with UV and
  VIS LEDs.
• During 80 days per year eclipses of max 18 min
  will occur allowing to perform occultation
  analysis.

ROB
Red (MSM) and Blue (PN) - left axis Synthesis of
May-June 04 PTB measurements of LYRA detector
response Dashed curves - right axis Filter
transmittances (Herzberg, Ly-?, Al and
Zr) Shadows - units not shown for clarity Solar
minimum and solar maximum spectra used as
references
LYRA SCIENCE
The PiN devices exhibits a rejection of circa 5
orders of magnitude between 200 nm and 400 nm.
The MSM rejection is around 4 orders. These
values are sufficient in amplitude. The
wavelength cut-off (220nm) is very appropriate
for the Herzberg channel, but too high otherwise.
Good rejection of the 200nm range is required
from the filters. VUV tests and absolute
calibrations were made at the Berlin Electron
Storage Ring (BESSY) thanks to a collaboration
between MPS and PTB (Physikalisch-Technische
Bundesanstalt, Germany).

• Solar physics
• In the LYRA timeline, discriminating all temporal
  features from noise
• Identifying the above events in the SWAP data to
  determine their spatial location and nature
  (flares but also others)
• Enhancing the accuracy at which the UV solar
  spectrum is measured, also in view of long-term
  monitoring
• Inverting the observations to produce
  best-guess UV solar spectra
• Looking for high-cadence chronology of events
  (typically flares) in the 4 LYRA channels, for
  their causality, impulsive phase, etc,
• Aeronomy
• Atmospheric composition analysis by the
  occultation technique (O2, O3, N2, etc...)
• Monitoring of the middle- and high-atmosphere
  response to solar activity
• Observation of the Polar Mesospheric Clouds
• Improvement of the climate-chemistry models
• Space Weather application
• Automated reporting of flares. Attempt to
  calibrate the LYRA data according to the C, M, X
  flare nomenclature originally defined in the
  X-rays

STATISTICAL DATA ANALYSIS

• LYRA will produce high cadence data (50 Hz) in 4
  UV passbands. To fully exploit the wealth of
  these data, statistical tools are needed. In
  particular, it is important to analyze small
  scale phenomena, and to exploit the multivariate
  aspect of the time series.
• Challenges
• Stabilization of the variance and denoising
  although the noise is expected to be small, it
  will not be Gaussian. Time series can be subject
  to photon noise, readout noise, as well as
  aliasing. The Data-Driven Haar-Fisz transform
  proposed by Fryzlewicz Delouille (2005) is able
  to (approximately) gaussianize a signal under
  very mild conditions on the noise distribution.
  Once the variance is stabilized, we can threshold
  the discrete wavelet coefficients to estimate the
  underlying signal
• Extraction of 'events' (even at small scales)
  with as least arbitrary as possible. Different
  definitions of event leads to different
  distributions of duration, energy, waiting time
  (cfr Buchlin et al, 2005)
• Multivariate analysis cross-correlation,
  alignment (wraping) of the different passband
  curves (work of J. Bigot, J. Ramsay).

Wraping fct that aligns 2 GOES signals

• LYRA will
• Benefit from innovative UV diamond detectors
• solar blindness
• radiation-hardness
• Benefit from ultraviolet in-flight calibration
  LEDs
• Technologically assess detectors, LEDs and
  filters in-flight stability/robustness
• Assess UV irradiance radiometers capabilities
• Take advantage of high-cadence observations 50
  Hz

(10-5)
(10-6)
CONCLUSION
Test on GOES data Denoising, Alignment of curves
(10-5)
(10-6)
Denoising using discrete Daubechies wavelet and
hard thresholding
Alignment of GOES long (0.1-0.8nm) and GOES
short (0.05-0.4nm) for a same period using
landmarks of J. Bigot and wraping fct of J.
Ramsay.