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The surface of ice satellites with known subsurface oceans (e.g., Europa, Ganymede, Callisto, Enceladus and Titan) are likely to contain the compositional imprints of the underlying interior ocean and their radiation processed products [1][2]. For instance, the community consensus is that Europa harbors liquid water beneath an icy crust, which has raised the possibility that life, or conditions favorable for life exist. Here we present the evolution of a powerful instrument “In situ Chemistry Experiment - μscope, Photoluminescence and Raman OBservations on Icy Satellites (ICE-μPROBIS),” a derivative of an instrument [3] proposed for a past NASA ROSES ICEE-2 AO, that can detect life biosignatures. The current Europa Lander Mission concept [4] with its advanced sample collection and analysis system, will be a blueprint for future lander/rover missions to other ocean worlds. ICE-μPROBIS instrument onboard the next generation of lander or rover mission will provide the unprecedented opportunity to carry out time-resolved Raman and photoluminescence (PL) spectroscopy, of ice samples collected from the surface, to discover if present, the types and distribution of biotic and abiotic organic compounds, measure CHNOPS containing organics and minerals and correlate them to radiolysis processed and textural features. ICE-µPROBIS includes an optical microscope to provide context imaging for the spectroscopy. Here, we describe ICE-μPROBIS’s capabilities and discuss time-resolved Raman and luminescence spectra of amino acids [5], PAHs [6] and, hydrated sulfates minerals and sulfuric acid [7] on the surface and subsurface of water-ice samples. Fig. 1. ICE-μPROBIS concept and system block diagram. ICE-µPROBIS enables in situ, spatially resolved and highly sensitive detection and characterization of organics and minerals from samples collected from icy satellite surface and near subsurface. Fig. 2. ICE-μPROBIS enables measurement of Raman spectra of the four aromatic amino acids at 5 m distance, L-phenylalanine (Phe), L-tyrosine (Tyr), L-tryptophan (Trp), L-histidine (His), and one aliphatic amino acid L-proline (Pro) [5]. Fig. 3. Standoff (120 m) TR-Raman spectra of Napthalene (PAH) inside water ice. ICE-μPROBIS will provide new insight into icy satellite surface processes by obtaining detailed analyses of surface composition. It can be used to identify key radiation products and structural changes in the sample, thus providing an indication of the extent of chemical and physical change and an estimate of the resurfaced age of the ice [6]. Fig. 4. Remote TR-Raman spectra at a distance of 5 m: a) ice nodules of 1 M sulfuric acid (H2SO4), and b) particulate ice solution of 3% hydrogen peroxide (H2O2) in distilled H2O in a lighted laboratory setting [7]. [1] Brown, M. E., et al., (2013). The Astronomical Journal, 145(4) [2] Vance, S. D., et al., (2021). Journal of Geophysical Research: Planets, 126, e2020JE006736. [3] Aslam, S., et al., (2020). AGU – iPosterSessions.com. Available online: https://www.researchgate.net/publication/346654802 [4] https://www.lpi.usra.edu/opag/meetings/opag2020fall/presentations/Hand_6014.pdf [5] Acosta-Maeda, T., (2016). Ph.D. Dissertation, https://scholarspace.manoa.hawaii.edu/bitstream/10125/51470/2016-08-phd-acostamaeda_uh.pdf [6] Sharma, S. K., et al. (2020). J. Raman Spectrosc. 51, 1782-1793. https://doi.org/10.1002/jrs.5814 [7] Sandford, M., (2020). PhD Dissertation, https://www.soest.hawaii.edu/gg/academics/theses/Sandford_Dissertation.pdf

From the Ice Giants Pre-Decadal Survey Mission Report 2017 (IGPDS), a Net Flux Radiometer (NFR) was identified in the IGPDS report as a complementary payload for a probe mission to the Ice Giants. In this paper, we will focus on the electrical architecture of an advanced NFR that is applicable to both Uranus and Neptune. The NFR contains seven spectral channels to measure energy flux from 0.2-300 μm region. The NFR rotates clockwise and anti-clockwise at 5 different viewing angles sequentially and each channel projects an unobstructed 5° field-of-view (FOV) into the atmosphere. It would enable the scientists to determine an ice giant’s atmospheric heat balance and the tropospheric 3D flow which will lead to deeper understanding the plant’s radiation, region of solar energy deposition and the atmospheric conditions [1], [2], [3], [4]. In this design, thermopile sensors are used as the detector to convert radiation energy to electrical signal. Those thermopiles are uncooled and passive detector which help to reduce overall size, weight and power (SWaP) factor of the instrument. However, the readout noise is dominated by low-frequency noise which limited the resolution of the instrument. To overcome such problem, an application specific integrated circuit (ASIC) with multi-channel analog-to-digital converter has been developed to reduce the low frequency noise of the readout system. A field-programmable-gate array (FPGA) has been integrated to the readout system to truly sample seven channels of the ASIC simultaneously. In this paper, we will go over the details of the ASIC and how to use it with the FPGA to implement the readout system for the advanced NFR. Figure 1 shows the system block diagram of the instrument [5], [6], [7]. Figure 1: System block diagram of the instrument [1] Aslam, S., et al., (2019). International Planetary Probe Workshop 2019, Oxford, UK [2] Aslam, S., et al., (2020). Space Science Reviews, 216(1) [3] Aslam, S., et al., (2018). 49th Lunar and Planetary Science Conference 2018, The Woodlands, Texas, USA, Volume: LPI Contrib. No. 2083, 2675 [4] Aslam, S., et al., (2021). EPSC Abstracts Vol. 15, EPSC2021-144, 2021 European Planetary Science Congress 2021 [5] Tran, D., et al., (2020). Sensors and Systems for Space Applications XIII 11422, 1142205. [6] Tran, D., et al., (2020). Lunar and Planetary Science Conference, 1233. [7] Quilligan, G., et al., (2021). IEEE Transactions on Nuclear Science.

We present the evolving design of an Ice-Giants Net Flux Radiometer (IG-NFR) [1][2][3], onboard a probe, Fig. 1, for in-situ measurements of the upward and downward heat flux in seven spectral channels as a function of altitude/pressure. These in situ probe measurements, will improve our understanding of energy balance and interior heat flux [4] and provide a reference profile to lift ambiguities inherent to remote observations [5]. The IG-NFR, Fig. 2, is designed to (i) accommodate seven filter bandpass channels (ii) measure up and down radiation flux in a 10° FOV for all channels in parallel; (iii) measure a change of flux of at least 0.5 W/m2 per decade of pressure; (iv) view five distinct view angles (±80°, ±45°, and 0°); (v) use application specific integrated circuit technology for the detector readout; (vii) be able to integrate radiance for 2 s or longer, and (vi) sample calibration targets every 19 s (assuming 100 m/s descent rate). Uncooled thermopile detectors are chosen for good detection sensitivity of radiation flux. A close hexagonal packing arrangement of Winston cones gives seven channels, with each Winston cone designed to give a 10° clear FOV. The Winston cone non-imaging optics, detectors and filters are all housed in a micro-vessel with CVD diamond and sapphire windows. The evacuated micro-vessel mitigates rapid excursions of temperature during the probe descent. A stepper motor with the aid of a gearbox rotates the micro-vessel, to each of the five view angles, so that the micro-vessel diamond windows have an unobstructed view through apertures in the mechanical enclosure into the atmosphere. The mechanical enclosure accommodates five apertures, hot and cold targets for radiometric calibration for each sequence of measurements (5-views). [1] Aslam, S., et al., (2018). 49th Lunar and Planetary Science Conference 2018, The Woodlands, Texas, USA, Volume: LPI Contrib. No. 2083, 2675 [2] Aslam, S., et al., (2019). International Planetary Probe Workshop 2019, Oxford, UK [3] Aslam, S., et al., (2020). Space Science Reviews, 216(1) [4] Irwin, P. G. J., et al., (2020). EPSC 2020-306, online [5] Mousis, O., et al., (2018). Planetary and Space Science 155:12-40

Icy worlds of the outer solar system contain tantalizing evidence of habitability and potential life. These bodies also present extra exploration challenges due to the harsh environmental conditions at the surfaces. Thus, robust and reliable detectors are necessary for the in situ spectroscopic identification of astrobiologically relevant compounds deposited on the icy surface, entrained in thick atmospheres, or rafted in plumes. In addition, the distinction between prebiotic, extant, and relict organic molecules in such environments is needed to address life detection goals. The Ultra-Violet Detector Innovation for Raman Exploration and CharacTerization (UV-DIRECT) of ocean worlds project focuses on the development SiC- avalanche photodiode (APD) technology for UV-Raman spectroscopy and Raman imaging. Si-based Single Photon Avalanche Diodes (SPADs) have been developed for time resolved Raman spectroscopy in recent years, but SiC (Silicon Carbide) APD detectors have advantages over them. Our detector is an ultra-compact, radiation and temperature tolerant, visible blind device that has high quantum efficiency (QE) in the DUV (~260 nm) but poorer performance in the near ultraviolet (NUV) between 300-340nm that is important for Raman Spectroscopy. Our approach to improve this combines a series of numerical models with laboratory testing to enhance the QE response and ultimately the single photon detection efficiency in the NUV (~340 nm). Raman spectroscopy has established itself in current missions as an information-rich, non-contact, non-destructive method for identifying and characterizing inorganic and organic compounds in a wide variety of planetary materials. UV/NUV-Raman spectroscopy is well-suited to characterizing plume materials and surface ice deposits, since it especially sensitive to organic compounds and inorganic salts improved sensitivity due to the combination of resonance effects and the lack of background fluorescence and less risk of sample damage compared to excitation with wavelengths Figure 1. UV-DIRECT is based on SiC-APD technology with the goal of pushing the capabilities of UV-Raman spectroscopy and Raman imaging for the exploration of icy worlds.

The NASA Ice Giants Pre-Decadal Survey Mission Report (2017) recommended the high scientific importance of sending a mission with an orbiter and a probe to one of the Ice Giants, with preferential launch dates in the 2029-2034 timeframe. Such a mission concept is equally well supported by European scientists and Mousis et al (P&SS, 155, 12, 2018) give compelling scientific rationales for the exploration of these worlds with missions carrying in situ probes. In this presentation we will outline the conceptual design of the Advanced Ice Giants Net Flux Radiometer (IG-NFR) instrument, currently being designed by NASA Goddard Space Flight Center to make in situ observations of the upward and downward fluxes of solar and thermal radiation in the atmospheres of Uranus and Neptune. The IG-NFR is designed to: (i) accommodate seven filter bandpass channels in the spectral range 0.25-300 µm (ii) measure up and down radiation flux in a clear unobstructed 10° FOV for each channel; (iii) use thermopile detectors that can measure a change of flux of at least 0.5 W/m2 per decade of pressure; (iv) view five distinct view angles (±80°, ±45°, and 0°); (v) predict the detector response with changing temperature environment; (vi) use application-specific integrated circuit technology for the thermopile detector readout; (vii) be able to integrate radiance for 2s or longer, and (vii) sample each view angle including calibration targets. The IG-NFR system noise equivalent power at 298 K is 73 pW in a 1 Hz electrical bandwidth. We present initial simulations of the anticipated observations using two radiative transfer and retrieval tools, NEMESIS (Irwin et al., JQSRT, 109, 1136, 2008) and the Planetary Spectrum Generator (PSG, Villanueva et al., 2017, https://psg.gsfc.nasa.gov). For the NEMESIS modelling the radiative fluxes observable at varying pressure levels were calculated with a Matrix-Operator plane-parallel multiple-scattering model, using between 5 and 21 zenith angle quadrature points and up to 38 Fourier components for the azimuth decomposition. We also employed PSG to further validate our flux estimates, providing an important benchmarking and comparison test between both models. PSG solves the scattering radiative transfer employing the discrete ordinates method, with the scattering phase function described in terms of an expansion in terms of Legendre Polynomials. Molecular cross-sections are solved via the correlated-k method employing the latest HITRAN database (Gordon et al., 2017), which are completed with the latest collision-induced-absorption (CIA, Karman et al., 2019), and UV/optical cross-sections from the MPI database (Keller-Rudek et al., 2013). For the nominal case the Sun was assumed to be at an altitude of 10° above the horizon. The internal radiance field was calculated at each internal level for a standard reference Uranus atmosphere (e.g., Irwin et al., 2017) with the addition of a single cloud layer, based at 3 bar and composed of particles with a mean radius of 1.0 µm (and size variance 0.1) and assumed complex refractive index of 1.4 + 0.001i at all wavelengths. The opacity and fractional scale height of this cloud were fitted in both models to match the combined near-infrared observations of HST/WFC3, IRTF/SpeX and VLT/SINFONI analyzed by Irwin et al. (2017). The internal radiance fields were calculated from 0.4 to 300 µm using this atmospheric model. We will show how these simulations are being used to guide the choice of spectral filter bandwidths and centres to optimize the scientific return of such an instrument. We will show that observations with such an instrument can be used to constrain effectively the radiation energy budget in the atmospheres of the Ice Giants and can also be used to determine the pressures of cloud and haze layers and broadly constrain particle size. Such modelling also allows us to simulate the visible appearance of Uranus’ atmosphere during a descent and to perform detailed validations of the simulations by comparing the two radiative transfer models (NEMESIS and PSG).

In this presentation we will describe recent work to model upward and downward fluxes of solar and thermal radiation in the atmosphere of Venus using the NEMESIS radiative transfer and retrieval tool (Irwin et al., JQSRT, 109, 1136, 2008). Using a plane-parallel matrix operator multiple-scattering model we simulate the internal 3D radiation field within Venus’ atmosphere and compare our simulations with the observations of the Pioneer Venus and Venera 13 and 14 entry probes. Such simulations allow us to assess the availability of sunlight and the visibility of the sun azimuth direction in the cloud layer for potential balloon missions, and also enables us to predict at what altitude the surface will become visible for probes descending on dayside. A reanalysis of the Venera 13 and 14 radiance spectra observations will be used to reassess earlier estimates of cloud structure and water vapour abundance. Such modelling also allows us to simulate the visible appearance of Venus’ atmosphere during the descent of a probe mission as will be shown.