Detectors are very often a performance-limiting component for space instrumentation – the better the detector, the better the instrument performance. Consequently, the European Space Agency (ESA) invests significant resources into the development of high-performance detector solutions for current and future missions. While technology developments span the full electromagnetic spectrum, infrared (and visible) wavebands are of particular interest and this paper presents a detailed overview of infrared detector development activities currently being undertaken by ESA in collaboration with European industrial partners.
To mitigate risks due to laser-induced contamination (LIC) for the LISA space mission, we have carried out an extensive LIC test campaign, including a series of short duration tests with different test parameters, as well as a long-duration test. Those previous experimental results as well as theoretical considerations indicate that LIC might be less of a concern for the LISA mission. A remaining concern is whether LIC could occur in the presence of metallic particles on optical surfaces and whether a higher pressure does have an impact. Our ongoing research thus aims at testing for a possible deposit formation in a combined LIC and metallic particulate contamination test. Therefore, a HR optics is contaminated with metallic (aluminum) particles, mounted in the sample holder and tested within a similar test setup used for previous tests. The test is performed at a pressure similar to the actual expected pressure of 10-5 mbar at the optical bench during the mission (previous tests at 10-8 mbar). These tests do not indicate that LIC is a concern and metallic particulate contaminants seem not to accelerate or trigger LIC in this laser regime.
KEYWORDS: Equipment, Calibration, Short wave infrared radiation, Design and modelling, Signal to noise ratio, Modulation transfer functions, Thermography, Tunable filters, Optical filters, Telescopes
The Land Surface Temperature Monitoring (LSTM), part of the expansion missions of the Copernicus programme, aims at providing data for land surface temperature and evapotranspiration at unprecedented spatio-temporal resolution, with the main objective of providing valuable data for improved water management at individual European field scale. This paper gives an overview of the instrument main requirements flowing down from the mission objectives, and the instrument design selected to fulfill them. The technical challenges are described as well as the key performances.
We investigate effects of laser-induced contamination (LIC) with contaminant materials and laser parameters relevant for the LISA space mission. To accelerate outgassing and a possible deposit formation, the contaminant materials have been heated to a temperature of up to 100 °C (nominal operating temperature of 20° C), and LIC tests were performed with a laser power density of up to 300 W/cm2 (to be compared with expected 125 W/cm2). Neither in-situ measurements (laser transmission, polarization and wavefront), nor a careful microscopic inspection of the optical surfaces after the LIC tests showed indications of a laser-induced deposit formation. Condensation on optical surfaces could be observed. This is cautiously encouraging for LISA and indicates that the LIC concern may be reduced compared to what observed at shorter wavelength or with pulsed laser radiation.
Additional presentation content can be accessed on the supplemental content page.
KEYWORDS: Equipment, Signal to noise ratio, Calibration, Short wave infrared radiation, Modulation transfer functions, Design and modelling, Astronomical imaging, Thermography, Tunable filters, Telescopes
The Land Surface Temperature Monitoring (LSTM), part of the expansion missions of the Copernicus programme, aims at providing data for land surface temperature and evapotranspiration at unprecedented spatio-temporal resolution, with the main objective of providing valuable data for improved water management at individual European field scale. This paper gives an overview of the instrument main requirements flowing down from the mission objectives, and the instrument design selected to fulfill them. The technical challenges are described as well as the preliminary predicted performances.
Additional presentation content can be accessed on the supplemental content page.
Flash Imaging LiDARs (Light Detection and Ranging) are active systems that resolves depth in a scene by time-of-flight measurements and are being seen as a competitive technological alternative that presents great advantages in the space scenario. The system records full 3D-images with a single laser pulse, thus eliminating the need for a scanning device.
A first step to improve the overall quality of the measurements is the calibration of the camera. There is a vast literature and well-stablished techniques concerning radiometric calibration (2D information). However, for time-of-flight (3D information) the subject remains open to improvement and dependent upon the specific characteristics of the detector. In this article we propose a calibration scheme for CEA-LETI’s LiDAR that combines both intensity, range accuracy and range precision calibration and presents the first enhanced results based on data acquired under laboratory conditions.
This project is a partnership between ESA and CEA-LETI aiming the design of a LiDAR system based on a custom MCTAPD FPA (Avalanche PhotoDiode Focal Plane Array) detector developed by CEA-LETI and the formulation of a set of imaging processing algorithms. The target is to demonstrate the potential of such detector technology and to evaluate the performances of the full system chain in the frame of the targeted application. In the future, a validation campaign on a real terrain, at ESA’s campsite, will be performed to demonstrate the system in a close-to-real configuration.
Detectors play a crucial role for the instrument design and the achievable instrument performance. The wavebands of interest for remote sensing are the visible and the infrared. Therefore, the European Space Agency has a strong interest in the performance enhancement of detector arrays in those spectral ranges. The Agency follows a continuous development strategy to enhance the capabilities for future Earth observation and astronomy missions. This paper presents the technical and planning status of these detector technology development activities.
As a consequence of the ongoing interest for deployment of laser systems into space, suitable optical components have to be developed and must be extensively space qualified to ensure reliable, continuous, and autonomous operation. The exposure to space environment can adversely affect the longevity of optics, mainly coatings, and lead to system degradation.
This paper summarizes our results of S-on-1 testing carried out over the last few years. Our experimental data sets were
taken with nanosecond laser pulse durations. An attempt was made to use the same scaling laws with femtosecond pulse
widths but it was not successful. The conclusion was made: there is no single model than can universally applied to all
kinds of survivability curves. We present this summary with a particular goal of making recommendations to those
involved in the periodic review of ISO 21254. A preliminary review of models, describing damage threshold evolution
with respect to incident laser pulses, is made.
L. Mondin, D. Wernham, F. Era, H. Kheyrandish, A. Bolkhovitinov, A. Baselga Mateo, A. Ciapponi, C. Heese, T. Ivanov, M. Hippler, D. Thibault, G. Van Papendrecht, W. Riede, Y. Butenko, H. Schröder
During the Aeolus laser and instrument transmitter development it was shown that atmosphere quality was one major limiting factor for high energy UV laser operation at ambient pressure. As already proven in literature operation can only be safely obtained in the presence of oxygen ([1] to [6]).
The Aladin instrument will fly on the European Space Agency’s ADM Aeolus satellite. The instrument is a Doppler wind
LIDAR, primarily designed to measure global wind profiles to improve the accuracy of numerical weather prediction models.
At the heart of the instrument is a frequency stabilized 355nm laser which will emit approximately 100mJ of energy in the
form of 20ns pulses with a fluence around 1Jcm-2. The pulse repetition frequency is 50Hz meaning that Aladin will eventually
have to accumulate 5Gshots over its 3 years planned lifetime in orbit. Due to anomalies that have occurred on previous spaceborne
lasers, as well as a number of failures that we have observed in previous tests, an extensive development and verification
campaign was undertaken in order to ensure that the Aladin instrument is robust enough to survive the mission. In this paper,
we shall report the logic and the results of this verification campaign.
In this work tests for determination of ablation thresholds of various ceramic materials for pulsed laser irradiations at
wavelengths of 355 nm and 1064 nm in vacuum are presented. For comparison tests with copper and aluminium are also
reported. The ablation process was monitored insitu by long-distance microscopy. The morphology of ablation spots was
exsitu inspected by scanning electron microscopy. Furthermore, the redeposition of potentially released particles on
optics in the vicinity to the target was examined.
The European Space Agency has a very strong interest in the performance enhancement of detector arrays for future scientific and astronomy missions. Improvements in Visible and Infrared wavelengths are of particular interest and the Agency undertakes a programme of continuous development aimed at enhancing the capability of detectors in these wavebands. This paper presents the status of these detector technology development activities.
The EUSO (Extreme Universe Space Observatory) project is developing a new mission concept for the scientific
research of Ultra High Energy Cosmic Rays (UHECRs) from space. The EUSO wide-field telescope will look down
from space onto the Earth night sky to detect UV photons emitted from air showers generated by UHECRs in our
atmosphere. In this article we concentrate on the mitigation strategies agreed so far, and in particular on the
implementation of a careful early selection and testing of subsystem materials (including optics), design and interfaces of
the subsystem and an optimization of the instrument operational concept.
Remote sensing is a priority activity for the European Space Agency and detector performance is a crucial factor in determining how well this role is performed. Consequently, the Agency has a strong interest in continuous improvement of both detector capabilities and availability within Europe. To this end, ESA maintains a number of strategic detector development plans combining both technology-push and technology-pull. The visible and infrared wavebands are of particular interest for remote sensing activities and this paper sets out the requirements for current and future missions and presents details of the Agency’s current and planned detector developments.
In this paper we will discuss the challenges of performing comparable laser damage testing as well as a detailed analysis
of the measurements conducted on the samples for this harmonisation activity. The goal of the activity is to enlarge the
test capacities within ESA’s EarthExplorer space program, especially for the missions ADM Aeolus [5] and EarthCare
[6], both having as main payload instruments containing high energy diode pumped nanosecond lasers. Four samples
have been compared with the S-on-1 method according to ISO21254-2, two AR1064/0° windows and two silicon wafers
leading to an agreement of better than 20% concerning the S-on-1 damage threshold.
In this paper, we report on a continuing multi-year empirical investigation into the nature of the laser
survivability curve. The laser survivability curve is the onset threshold as a function of shot number. This
empirical investigation is motivated by the desire to design a universal procedure for the measurement
of the so-called S on 1 damage threshold. In this year’s paper we investigate the usefulness of scaling
the fluence with shot number. First the scaling process is defined and applied to a result from our
experimental archives. The probability of damage curve for a single shot test is extrapolated to 104
shots. The scaled result is shown to be very close the observed results providing a basis for extrapolation
to very large values of n.
This paper presents a first look at the application of maximum likelihood estimation methods to S on 1
testing by comparing results with an analysis that is typical of our previous reports and consistent with
ISO 21254. In traditional, ISO tests, the data collected from an S on 1 test is processed to give a set of
fluences representing the no-damage or safe operating fluence (SOF) as a function of the number of
shots. The (SOF,N) ordered pairs are then fitted to a model and the model is used to extrapolate the SOF
to large values of N. In the present report, the entire data set from an ISO S on 1 test is processed via
maximum likelihood methods to estimate the probability curve as a function of fluence, P(Φ). The
probability of survival to N shots is calculated, under the assumption that P is independent of N, to give
the final results. The maximum likelihood method shows promise for application to S on 1 testing.
To cover the preparatory test issues of upcoming ESA space laser missions, in joined effort amongst various
laboratories, an adaptation of existing laser damage test benches has been performed. Conventional S-on-1 tests were
extended with raster scanning procedures. Various aspects of characteristic damage curve issues are discussed.
Sensitive surface analysis like time-of-flight SIMS is used to identify potential low density low damage threshold
precursors. The inter-correlation of flight module testing and preceding single component testing is demonstrated.
Finally, the successful execution of a flight module endurance test with more than 200 Mio. shots is detailed.
In the determination of the laser-induced damage threshold (LIDT) of optical coatings former Round-Robin experiments
stand as the empirical foundation for the development of the International Standard as it is known today. In 1983 and
1997 such experiments were conducted at the fundamental wavelength of the Nd:YAG laser under atmospheric
conditions settling the International Standard as it is known today.
To cope with the growing demand of LIDT testing for satellite missions, existing test methods have to be extended to
deal with operation in space-like environments. This requires LIDT measurements performed under customized vacuum
conditions to validate the laser resistance capability and estimate the life time of optical components. To foster the
quality of measurements in such environments the need for an inter-laboratory comparison in vacuum conditions
emerged.
In this paper, we give the third installment of our ongoing investigation into the nature of the laser
survivability curve (LSC). In this year’s report, We examine a set of identically polished samples coated with
the same AR coating design. One set coated using IAD process and the other e-beam. In the samples
investigated show similar asymptotic behavior within manufacturing methods, but each technique behaves
differently.
In this paper, we report on the second installment of our ongoing investigation into the nature of the
laser survivability curve (LSC). The LSC has been traditionally viewed as a curve in the plane defined by
fluence,φ , and the number of shots, N, which defines the frontier of assured survival. In this year's
report we expand the concept of the survivability curve to a surface of survival, the laser survival surface
(LSS), which is in turn used to develop a conditional probability estimate for survival. This conditional
probability viewpoint is discussed as a possible basis for a
cost-efficient life time test. The LSS is
developed for test results at 1064 nm wavelength taken at atmospheric pressure and at vacuum.
Reliable, long term operation of high-power laser systems in the Earth orbit is not a straightforward task as the space
environment entails various risks for optical surfaces and bulk materials. The increased operational risk is, among others,
due to the presence of high energy radiation penetrating the metallic shielding of satellites and inducing absorption centers
in the bulk of optical components, and vacuum exposure which can deteriorate coating performance. Comprehensive testing
for analyzing high-energy radiation effects and mitigation procedures were performed on a set of frequency conversion
crystals and are discussed in this paper. In addition to a general resistance to space environmental effects, the frequency
conversion crystals were subjected to a comparative analysis on optimum third harmonic efficiency, starting from pulsed
1064 nm laser radiation, with the goal of exceeding a value of 30%. Concomitant modeling supported the selection of
crystal parameters and the definition of crystal dimensions.
The mechanism of laser induced damage in optical materials under high power nanosecond laser irradiation is commonly
attributed to the presence of precursor centers. Depending on material and laser source, the precursors could have
different origins. Some of them are clearly extrinsic, such as impurities or structural defects linked to the fabrication
conditions.
In most cases the center size ranging from sub-micrometer to nanometer scale does not permit an easy detection by
optical techniques before irradiation. Most often, only a post mortem observation of optics permits to proof the local
origin of breakdown.
Multi-scale analyzes by changing irradiation beam size have been performed to investigate the density, size and nature of
laser damage precursors. Destructive methods such as raster scan, laser damage probability plot and morphology studies
permit to deduce the precursor densities. Another experimental way to get information on nature of precursors is to use
non destructive methods such as photoluminescence and absorption measurements.
The destructive and non destructive multiscale studies are also motivated for practical reasons. Indeed LIDT studies of
large optics as those used in LMJ or NIF projects are commonly performed on small samples and with table top lasers
whose characteristics change from one to another. In these conditions, it is necessary to know exactly the influence of the
different experimental parameters and overall the spot size effect on the final data.
In this paper, we present recent developments in multiscale characterization and results obtained on optical coatings
(surface case) and KDP crystal (bulk case).
In this paper, we report on the first steps in an empirical investigation into the nature of the laser survivability curve.
The laser survivability curve is the onset threshold as a function of shot number. This empirical investigation is
motivated by the desire to design a universal procedure for the measurement of the so-called S on 1 damage
threshold. Analysis is carried on the test results for first results from a large set of planned measurements from
identical samples produced for this investigation. The sample set and test conditions are discussed. A pair of
measurements, one taken at atmospheric pressure and one at vacuum are introduced and analyzed as an example.
Interim observations on the nature of the laser survivability curve, and its determination to be used in the remainder
of this investigation based on this initial look, are presented at the conclusion of this paper.
In this paper, we present test results and involved procedures of a comprehensive test campaign for S on 1 testing of laser
optics with large test areas allowing the generation of a profound test database for further analysis. This database will serve
as a starting point for an empirical study of the lifetime of laser optics, which will be discussed in companion paper
somewhere in these proceedings.
The optics are designed to operate as anti-reflective or high-reflective components at the respective test wavelengths for 0° angle-of-incidence. Both, coatings and substrates of 2.0 inch diameter are produced from the same batches to be as identical
as possible. There were two different coating technologies used, e-beam and IAD e-beam, to explore a possible effect of the
coating process on the long term laser irradiation behavior.
The laser damage test bench is operated with a laser source delivering laser pulses in a single longitudinal mode at a
repetition frequency of 100 Hz. The beam profile is of a
Gaussian-shape and of high spatial quality at the fundamental
Nd:YAG laser wavelength with a pulse duration of 3.5 ns at 1064 nm. Typical beam diameters on the samples were 400
μm, and usually more than 500 test sites are irradiated in one test to achieve statistical significance. The laser test procedure
itself is adapted from the ISO standard 11254-2 for multiple pulse irradiations, and the LIDT evaluation is done
accordingly.
KDP is a non linear optical crystal used for frequency conversion in high power applications. In this paper we present
results of optical non-destructive measurements on different fast growth KDP crystals in order to characterize the
precursors responsible for laser-induced damage. We performed two types of analysis: the first one is temporally
resolved photoluminescence excited by a pulsed Nd:YAG laser at 4.66 eV and 3.49 eV (266 nm and 355 nm). The
second is spatially resolved photothermal deflection pumped by a CW Argon laser at 3.53 eV (351 nm).
With these two complementary techniques we highlight the presence of large scale inhomogeneities and we discriminate
nano-scale defects statistically distributed in the bulk of the crystals.
The development of high power laser for large instruments such as LMJ and NIF, as well as the use of smaller optical structures with high densities of energy lead to consider laser induce damage threshold (LIDT) as a critical criterion in optical components development. Furthermore in the same time some applications need an increase of the lifetime of the laser source (up to 109 shots for spatial applications). In this context to improve optical components numerous studies are undertaken to determine the origin of laser damage
process. Through these studies, it is now commonly admitted that the first stage of the laser damage process in the nanosecond regime is caused by localized defects included in the material. In order to determine the laser damage threshold, it is necessary to perform a statistical study of damage on materials. This destructive technique beyond the determination of damage threshold allows to determine the density of precursor centers and to discriminate different kinds of precursors by using adapted beam sizes. However the nature and
therefore the origin of the defects remain unknown. In order to get information on this nature, non destructive tools have to be involved. Indeed on one hand photothermal microscopy permits to make measurement of the local absorption under irradiation, on the other hand, photoluminescence cartography and spectroscopy gives information on material composition. The coupling of the different techniques on a laser damage test set-up optimizes the chance to have a complete signature of precursor center and information about the mechanism of damage process. Furthermore, nondestructive diagnostic under mutilple irradiations permit to study "fatigue" and conditioning process.
Potassium dihydrogen phosphate (KH2PO4 or short KDP) is one of the major nonlinear optical crystals for frequency
conversion and electro-optic switching in high power lasers. In particular, this material has been chosen for the
frequency converters of the Laser Mega Joule in France and the National Ignition Facility in the US. These laser work
close to the damage threshold of the crystals and large efforts have been provided to improve the laser induced damage
threshold for KDP at different wavelength.
We present in this paper first results of a new setup dedicated to the correlation of non destructive luminescence
spectroscopy and destructive laser damage tests. We concentrate on the differences between conventionally grown KDP
and KDP-crystals that have been produced by the rapid growth method that has been developed in the last years
especially for the large laser installations LMJ and NIF. Different photoluminescence spectra are obtained from
conventionally and rapidly grown KDP for both pump configurations: (i) pulsed pumping by the forth harmonic of a
Nd:YAG laser at 266nm, and (ii) continuous pumping using a frequency doubled Argon ion laser at 244nm.
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