In this contribution, the detector-characterization results and some of the on-ground calibration plans are presented for an adjusted and improved SPEXone satellite instrument. SPEXone is a highly compact multi-angle space spectro-polarimeter developed by a Dutch consortium for the NASA PACE observatory scheduled for launch early 2024. This instrument will enable detailed characterization of the microphysical properties of fine particulate matter or aerosols in the atmosphere from low Earth orbit, which is essential for climate, ecosystem, and human-health science. A successor to the SPEXone instrument is currently being developed, with a wider swath as the main change (250 km instead of 100 km), and with several design improvements to reduce straylight. The detector firmware was adjusted to enable the required higher frame rate, and to make the readout more robust. The detector was characterized in a similar way as for PACE, though even more extensively based on lessons learned. In particular, full illumination measurements were complemented with partial illumination measurements, where parts of the detector are covered using dedicated detector masks, to investigate peculiar signal-induced offset effects that were observed only late for PACE. Additionally, direct memory measurements were performed using time-dependent illumination generated using a fast electronic shutter. Following the detector characterization, instrument-calibration preparations have started. The instrument will be fully calibrated in ambient, complemented with a highly selective set of measurements in vacuum. The approach followed will be similar to PACE, but modifications will be made to deal with the increased swath. Important improvements will be implemented to improve the data quality, such as increased number of wavelengths for straylight measurements.
Aerosol quantification is of paramount importance for climate research, health and many other fields. The best method for measuring and characterizing aerosol from space is the application of a multi-angle polarimeter. A Dutch consortium has developed and delivered the so called SPEXone instrument for the NASA PACE (Plankton, Aerosol, Cloud, ocean Ecosystem) mission, to be launched early 2024. SPEXone is based on the polarization modulation of the spectrum, allowing full characterization of the state of linear polarization of the incoming light. Earth is viewed under five angles, producing ten modulated spectra, projected on a single detector. A polarimetric accuracy of 0.3% is achieved, with the instrument of about 10 dm3 volume and 10 kg mass. Based on the SPEXone design and experience, an upgraded instrument is being developed. Main change is the wider swath applied, from the 100 km swath for PACE to the present 250 km. This impacts the five telescopes, being integrated in one telescope unit. Other changes in the design are based on lessons learned, in particular the reduction and avoidance of stray light. The detector readout is adjusted for higher frame rate and more robust readout. These changes do not impact the instrument's budgets for mass, volume and power. In this paper, we will explain the principle of the SPEXone multi-angle spectropolarimeter instrument, the improvements with respect to the PACE version and its development status. The instrument can be flown as a stand-alone instrument for aerosol detection, as well as a support instrument where aerosol corrections are relevant, e.g., for high accuracy detection and quantification of methane and CO2.
This contribution presents the on-ground characterization and video chain development of the CMOS detector implemented in SPEXone, the five-angle space spectro-polarimeter for the NASA PACE observatory scheduled for launch in 2023. SPEXone is a Dutch compact payload contribution developed in a partnership between SRON and ADSN, and supported by TNO. Making use of spectral modulation, this polarimeter will enable in-depth and global characterization of the microphysical properties of fine particulate matter or aerosols in the atmosphere from low Earth orbit. In SPEXone, the spectrally modulated images are captured by means of a commercial-off-the-shelf detector module (DEM) from 3Dplus, which is equipped with a CMOS image sensor with integrated front-end-electronics. Video chain developments, including DEM firmware, read-out, flexible binning and DEM interfacing through SpaceWire have been carried out in-house. Making use of the firmware, the optimal detector parameters with associated random noise, full-well capacity, and photo response non-uniformity (PRNU) of the DEM were determined by placing the DEM in front of an integrating sphere fiber-fed with a stable white light source with accurately adjustable intensity and a highly linear reference detector, providing highly uniform illumination of the whole detector area at well-known relative light intensities. The rationale behind the measurement sequences is explained, and the full-well and read noise performance under different gain settings is described. The full-well capacity of the DEM is found to be not constant, but increasing significantly with illumination intensity.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.