OPSE Demonstration Model: testbed and test review D. Loreggia, ALTEC, OPSE Demonstration Model: Testbed and Test review Davide Loreggia INAF – National Institute for Astrophysics Astrophysical Observatory of Turin

OPSE Demonstration Model INF/OATo Laboratory Dressing area ISO 5/6 Clean room Service grey room - 14 October 2015: OPSE DM delivery - 15 October 2015: OPSE DM INF/OATo Lab - End of October: Preliminary verification of the OPSE DM functionality - Mid December: Homogeneity tests results D. Loreggia, ALTEC, OPSE Demonstration Model: Testbed and Test review

Homogeneity test Homogeneity tests consisted in measuring the spatial profile of the OPSE LED emission along the two orthogonal direction, at different distances. The main task was to verify the compliance of the emission angle with requirement and the profile uniformity and stability [Ref: P3-INF-TN-15003_ OPSE_DM_Uniformity_Test v.0.3, G. Capobianco]. OPSE Demonstration Model pixels Image from OPSE LED OPTRANS VS575N (only for info) Temporal stability (after 3 min) : 0.15%.. D. Loreggia, ALTEC, OPSE Demonstration Model: Testbed and Test review

OPSE Demonstration Model Homogeneity test The set-up is composed by: - OPSE DM Led with the current controller; - A calibrated photodiode (Newport 818-SL), with a pinhole of Φ = 300 μm and an optical power meter (Newport 1830-C). The photodiode is mounted on a motorized translation stage Micos, with a range of 200 mm; - Digital multimeter (Keysight 34465A ) to monitor the resistance values Measurements repeated for 3 values of the forward current of the LED. For each current, horizontal and vertical scans are performed at 3 LED-Photodiode distances. The currents are: 2.5mA; 5mA; 20mA The LED-Photodiode distances are: 107 mm; 214 mm; 535 mm. D. Loreggia, ALTEC, OPSE Demonstration Model: Testbed and Test review

Homogeneity test – cont. Input current Distance (mm) H-Emission angle (deg) H –FWHM (mm) V-Emission angle (deg) V –FWHM (mm) H -T (°C) H - T.stab. (°C) V -T (°C) V-T. stab. (°C) 2.5mA 107± 5.4± 10.05± 5.3± ± ± ± 6.2± 23.15± 6.1± ± ± ± 6.7± 62.50± 6.7± ± ± mA 107± 5.2± 9.80± 5.1± ± ± ± 5.9± 22.25± 6.3± ± ± ± 6.3± 59.35± 6.7± ± ± mA 107± 5.1± 9.50± 5.4± ± ± ± 5.9± 22.12± 6.3± ± ± ± 6.2± 58.35± 6.9± ± ± 0.02 After first scan along one direction (X-axis) the OPSE Cup was rotated of 90° and the new measurement scan (Y-axis) was performed. The temperature stability of the OPSE DM was monitored, too [P3-INF-TN-15003_ OPSE_DM_Uniformity_Test v.0.3, G. Capobianco]. OPSE Demonstration Model D. Loreggia, ALTEC, OPSE Demonstration Model: Testbed and Test review

OPSE Demonstration Model Homogeneity test – cont. U = 1- [(Max – Min)/Max] D. Loreggia, ALTEC, OPSE Demonstration Model: Testbed and Test review

OPSE Demonstration Model OPSE metrology: accurate monitoring of the OPSE LED signal at focal plane level, while the OSC/CSC geometry is maintained in the expected FF configuration  centroiding of the OPSE PSF using a CoG algorithm [P3-INF-TN OPSE error budget analysis v1.3, D. Loreggia] OPSE Testbed Testbed design requirement: having the ASPIICS telescope in the laboratory to collect the light coming from the OPSE LED within same angle, with the same throughput as it was at the FF operating distance and with the same image dimension and position at the focal plane. Need to use a relay optics to mimic the space condition in lab  Solution: have a reverse Keplerian telescope in front of ASPIICS Telescope Reverse keplerian configuration + Barlow lens for objective EFL multiplication [P3-INF-TN OPSE DM testbed_v0.1, D. Loreggia] D. Loreggia, ALTEC, OPSE Demonstration Model: Testbed and Test review

OPSE Demonstration Model Requirement on angular magnification (having assumed the source in the lab at 2.5m) OPSE Testbed – input conditions Available optics for Objective INF: 1) achromatic doublet with EFL = mm 2) off-axis parabola with EFL = 2000mm EFL eye = mm Using a 10mm lens if must be a very fast lens (F#1.4). This is critical for alignment and optical quality over the field.  increasing the EFL eye  use a focal length multiplier, e.g., a Barlow lens, to increase the EFL obj D. Loreggia, ALTEC, OPSE Demonstration Model: Testbed and Test review

OPSE Demonstration Model RMS radius:  m Ima. coord.: (0 ; 0.254)mm RMS radius:  m Ima. coord.: (0 ; 0.509)mm OPSE LED at ISD OPSE LED at 2.5m in OATo lab with relay optics RMS radius:  m Ima. coord.: (0 ; )mm RMS radius:  m Ima. coord.: (0 ; )mm NOTE: best matching in terms of spot dimension is less demanding being possible to optimally fit the spot dimensions by changing the eyepiece-A-objective distance OPSE Testbed – simulations ElementsDistance [mm] Eyepiece – A A – Barlow Barlow – Objective We can realize a well suited F#3 eyepiece using the achromatic doublet LAO mm (EFL=40.5mm, aperture = 13mm), commercialized by Melles Griot. D. Loreggia, ALTEC, OPSE Demonstration Model: Testbed and Test review OPSE LED at 974mm in OPSYS with relay optics RMS radius:  m Ima. coord.: (0 ; )mm RMS radius:  m Ima. coord.: (0 ; -1.14)mm

OPSE Demonstration Model OPSE Testbed – radiometric balance The LED’s light at the ISD will be collected by the ASPIICS telescope pupil with diameter = 50mm. The solid angle  pupil at the LED is : The emission angle of the OPSE LEDs is ±6° so that the emission solid angle is.  LED = 2  [1-cos (  )] = str The effective collecting volume - CV - is obtained as: The collecting volume we will have in lab is constrained by the vignetting of the ASPIICS pupil on the eyepiece area Testing the CoG algorithm under the same in-flight SNR expected conditions will ask for tuning up the emission flux of about 30% D. Loreggia, ALTEC, OPSE Demonstration Model: Testbed and Test review

OPSE Demonstration Model OPSE Testbed – set up 1) OPSE DM testbed installed in the laboratory available at INF/OATo and 2) OPSE DM testbed installed at the INF/OPSYS facility, ALTEC, Turin. The optics design was developed assuming to have the OPSE DM testbed operating in two different laboratory configurations 1) at INF/OATo lab D. Loreggia, ALTEC, OPSE Demonstration Model: Testbed and Test review

OPSE Demonstration Model OPSE Testbed – set up at INF/OPSYS The OPSE DM is mounted on optical bench positioned at 90° with the SPOCC unit. The light from the OPSE is refocused by the eyepiece lens and injected into the Space Optics Calibration Chamber (SPOCC) via a folding mirror. The light enters the SPOCC through a window. We plan to locate the EFL multiplier before this window, to avoid any action inside the calibration chamber. The ASPIICS Telescope will be installed in the OPSYS where it is the optical bench. The SPOCC and the OPSYS interface via an hole in the wall that delimits the ISO 5 clean room (right area in the figure). At OPSYS we plane to have the tests with the flying telescope and all the sub-system (OPSE, SPS, diffraction,…) installed, for final acceptance. D. Loreggia, ALTEC, OPSE Demonstration Model: Testbed and Test review

The off-axis parabola that will be used as object lens, has EFL = 2000mm. With 3x Barlow lens we get an overall EFL of 6000mm that, from the equivalence of the angular magnification, yields to : OPSE Demonstration Model OPSE Testbed – set up at INF/OPSYS (cont.)  x = 974 mm x For both the configuration the best matching with the FF geometry is given with the OPSE DM (emitting LED) laterally shifted of 50mm from the optical axis. 100mm D. Loreggia, ALTEC, OPSE Demonstration Model: Testbed and Test review

OPSE Demonstration Model OPSE Testbed – Alignment procedure Individuation of the central axis of light propagation following the procedure described in [P3-INF-RP OPSE DM Uniformity Test_v.0.3], i.e., measurement of the emission profile at different distances in order to locate the centre of the emission envelope Reference flux measurement along the identified direction by measuring the flux at longer distances by finding the expected value scaled with the squared of the distance. Alignment of the eyepiece achromatic doublet (LAO_ mm [AD1]) looking for the eyepiece focus optimal position and dimensions (make reference to the expected values given by ZEMAX, in terms of spatial dimension and not for what concern the throughput) Barlow lens + the Object collimating element is inserted in the optical path at the expected distances [P3-INF-TN-15013_v0.0]. The light will exit the Objective with a divergence that will be measured by comparing the footprint of the beam at different distances  estimate the angle of divergence and compare it with the expected one given by the ZEMAX. D. Loreggia, ALTEC, OPSE Demonstration Model: Testbed and Test review

Once we will get the correct alignment of the relay optics we will insert the telescope. OPSE Demonstration Model OPSE Testbed – Alignment procedure The alignment of the telescope is an open point. INF assumed to be provided with the telescope assembled. In recent communication, CSL informed INF that the single pieces of the telescope will be send to INF and INF will be in charge of the alignment. We cannot expect to get the same image as expected. We will be provided with alignment tolerance and we will look for the best configuration in order to get best achievable PSF. At this point we will shift a part the source of 50mm, and we will start the image acquisition for a preliminary processing in order to check the effective spot dimensions and to have a verification of the image properties (PSF profile, throughput,...) and of the CoG centroiding performances. INF will be provided of the detector too, even if it will not be a DM of the flying one. The only commonality will be the pixel size of 10µm. The test on the CoG will be run with different spot image in order to have an empirical feedback of the sampling contribution to the centroiding error, for different spatial scale. D. Loreggia, ALTEC, OPSE Demonstration Model: Testbed and Test review

OPSE Demonstration Model OPSE Testbed – Tests Compare the flux entering the telescope with the output power from the OPSE DM in order to have an empirical evaluation of the relay optics efficiency (throughput). Compare these two measurements with the signal at CI focal plane to split the relay optics absorption contribution and the real telescope+detector efficiency/readout contribution. This in order to have a laboratory confirmation of the operation SNR contributions (devices calibration). Image acquisition changing the OPSE DM output power to check the detector and centroiding procedure and performances while the SNR changes. The reference input power we will be: 2.5mA, 5mA, 10mA, 20mA (TBC). One of the deliverables of this first test run will be the definition of the lower limit of the SNR for which the centroiding performances can be assumed acceptable (TBD) Measure the temporal stability of the OPSE LED. Repeating the same measurements described above with a 6hrs delay after having let the LED switched on in order to simulate OPSE measurement at beginning and at the end of the FF phase. Any other test will be considered useful (under consideration) D. Loreggia, ALTEC, OPSE Demonstration Model: Testbed and Test review

OPSE Demonstration Model OPSE Testbed – Tests (cont) The main task of the OPSE system is to detect any relative movement of the two spacecrafts. We consider the relay optics used in lab as a geometric-equivalent-device of the External Occulter and because of this, there is an absolute equivalence in moving the relay optics or the telescope. We will follow the second approach, having the telescope (both in OATO Lab and in OPSYS) mounted on a XYZ translation stage. The accuracy requirement in lateral movements of 0.3mm is achievable with micron-step motor (available at INF/OATo). The accuracy requirements for lateral measurement is 300  m that at focal plane level corresponds to 1.5  m, and 20cm for longitudinal movement. In [P3-INF-TN OPSE error budget analysis v1.3] we show that this accuracy requirements cannot be fulfilled mainly because of thermo-mechanical errors. In our test we do not consider all the external contribution but we will concentrate on the verification and validation of the CoG performances. Using the step motorized XYZ translation stage, we will move the telescope of the amount equal to the lateral and longitudinal accuracy requirements and we will check the capability of the CoG algorithm to retrieve the expected position of the OPSE DM image. This measurement is repeated changing the input power and, by consequence, the SNR. Input current: 2.5mA, 5mA, 10mA, 20mA. Test will be performed at ambient temperature only. D. Loreggia, ALTEC, OPSE Demonstration Model: Testbed and Test review

OPSE Demonstration Model OPSE Testbed – test schedule Relay optics pieces procurement Procurement of the achromatic doublet LAO mm used as eyepiece; Procurement of the 3X Barlow multiplier. TBD if to have it off-the-shelf or if it will be necessary to customize it. Because of the need to use it for diffraction test we plane to procure an achromatic one. We plane to start procurement in February. Time for procurement: TBD Test time schedule (Reference unit: weeks) T0: ASPIICS telescope + relay optics pieces at INAF/OATo T0+3: Telescope and OPSE DM testbed aligned (TBC) T0+4:OPSE DM test – first test run T0+5:OPSE DM test – second test run T0+6:OPSE testbed data analysis T0+7:OPSE DM testbed verification and validation report delivery (test data sheet included) The schedule for the OPSE DM tests is expected to merge with SPS DM testbed assembly and tests. The most of the effort and time will be required to realize the optimal alignment of the telescope and of the relay optics with the telescope. D. Loreggia, ALTEC, OPSE Demonstration Model: Testbed and Test review

OPSE Demonstration Model OPSE system and test review OPSE DM test bed description and alignment procedure both for INF/OATo Lab configuration and INF/OPSYS configuration The acceptance criteria for the tests will be the verification of the accuracy requirements for lateral and longitudinal relative movements between the OPSE and the telescope. We will tag the test as successful if the we will confirm the accuracy requirement retrieved by the CoG algorithm, under the condition discussed above. The expected SNR shall be confirmed too with a description of operation condition, test bed calibration procedure and results. Test deliverables will be the data sheet of any test input/output condition, the logbook of the test procedure, the report on the algorithm performances validation, the test results including test bed calibration Summary D. Loreggia, ALTEC, OPSE Demonstration Model: Testbed and Test review