Science Payload

Hypothesis, Objectives, Goals

• Space weathering processes occurs on short time scales, days to months

• We want to determine if space weathering is geology-dependent and visually detectable on short time scales

• We are going to measure changes in visual and spectral properties of geological materials and astromaterials relevant to a range of solar system bodies i.e. the moon and asteroids

Scientific Importance and Relevance

• Iris is the FIRST space mission to attempt to understand space weathering of geological materials

• Space weathering occurs on ALL airless bodies

• Space weathering impedes our ability to map the surface geology of these celestial bodies

• Relevant to understanding the evolution of asteroids Ryugu and Bennu – target asteroids of JAXA and NASA-CSA sample return missions (Hayabusa2 and OSIRIS-REx). The returned samples will provide ground truth for our mission

Past Space Weathering Experiments

• NASA’s Long Duration Exposure Facility (LDEF): 1984-1990 – long-term effects of space weathering in low-Earth orbit (LEO) on components, spacecraft materials, and operations/systems

• ESA’s European Retrievable Carrier (EURECA): 1992-1993 – 15 experiments in LEO (science and astronomy)

• Japan’s Space Flyer Unit: 1995-1996 – to test space-related technologies in LEO

• NASA’s Mir Environmental Effects Payload (MEEP): 1996 -1997 – a variety of materials in LEO were exposed to space debris impacts and the harsh space environment (materials used for the ISS)

• NASA’s Materials International Space Station Experiment (MISSE 1-8): 2001-2014 – to determine long-term space weathering effects of materials mounted on the outside of the ISS

Payload Activities to Date

• Recorded lighting geometry with a diffused light source to ensure homogenous radiation over the payload sample plate at various phase angles

• The magnitude of reflectance increase or decrease will be dependent on the angle of incidence

• Will expect to see variation in slope (i.e., decrease in shortest wavelength region) and in overall reflectance (darkening) while the CubeSat is in orbit

• Developed procedures on data processing for converting RGB values to visible reflectance spectra

Variation in Photometry Due to Geometry

Further Payload Characterization

• Will characterize flight lens for camera image quality

• Will characterize flight lens to produce spectra in the visible spectrum using data from the images

• Will record angle of incidence using a goniometer and diffused light source with the flight lens

• Will test engineering model (EM) lens with DUV radiation in a nitrogen environment, which provides illumination down to 150 nm

• EM lens similar model to flight lens

• The samples will undergo thermal vacuum (TVAC) testing when mounted onto the CubeSat prior to launch

• Will acquire UV-VIS-NIR reflectance on the samples while assembled in the sample plate

• Will compare UV-VIS-NIR reflectance to the visible spectra produced by the flight camera lens to check camera response

Sample Preparation

• Sample preparation procedure identical to that used for Mars Perseverance rover calibration targets

• Sample preparation done by same facility (CIRIMAT) that prepared the Perseverance rover SuperCam calibration targets

Outgassing

• All samples are vacuum sintered, performed at high temperatures, and applied pressures of typically 50 -100 MPa

• Method: Spark Plasma Sintering (SPS)

• As a result, should be sufficient to remove any volatiles so collected volatile condensable material (CVCM) and total mass loss (TML) risks are low (R-PLD-0400, R-PLD-0410)

• Due to the high temperatures and negative vacuum pressures, the samples would have outgassed any volatiles during the vacuum sintering process

• The samples are considered low risk and benign

• Total mass measurement for all 24 potential samples is 0.79% of the entire mass of the spacecraft

• All sample properties are known (XRF, XRD, Raman, and UV-VIS-NIR reflectance)

• Due to the low mass, and high-temperature vacuum sintering, we do not consider the geological samples to be of harm to the mission

Outgassing Plan

• The CubeSat with the geological payload fully assembled prior to launch will be subjected to TVAC testing

• During TVAC testing, the samples will be baked out at 45˚C for a period of time (RFD submitted) and are open to suggestions regarding time duration

• This will desorb any volatiles, including atmospheric water, that condensed on the sample surfaces since vacuum sintering

• Post-TVAC, samples will be stored in a controlled environment at Magellan Aerospace (in the repository in the cleanroom)

Data Acquisition

• Measuring red-green-blue (RGB) reflectivity of a range of geological samples relevant to multiple planetary bodies

• Using a three-colour commercial off-the-shelf (COTS) camera

• Two cameras will be included on the satellite for redundancy

• Multiple images were taken with the test lens to acquire images to test for camera response

• The data from these images have been converted from RGB values to absolute visible reflectance spectra

• The spectra will be used to calibrate in-orbit measurements of the optical properties of the samples to assess the effects of space weathering

• The images will also be used to measure changes in physical properties of the payload

Calibration Standards

• Three calibration standards will be used to determine detector response of RGB cameras pre-launch and during the mission

• Multiple calibration targets to be used: AluWhite98 (white reference), Grey33 (grey scale), and Green (colour standard), as well as a black aluminum standard (dark reference)

• Atomic oxygen (AO) is present in low-Earth orbit but not on planetary surfaces

• Will look into developing calibration targets that are resilient and not resilient to AO

• Will use them as controls to form part of the experiment by analyzing how the optical properties change between the two disks over time

• We will compare the pixel intensities to the calibration standards so that we remove the effect of any changes in camera response

• These materials have all been used in previous planetary missions (e.g., Mars Perseverance rover)

Mission Status for Science Experiment

• Several more samples have undergone vibration testing

• As a result of the pandemic, there is still a delay on receiving the last batch of samples from CIRIMAT

• To date, 17 samples passed testing and verification

• Only two candidate samples have failed testing: anthracite coal and goethite

• We are currently meeting the mission requirement of a minimum 10 samples for the payload (V-PLD-0010, V-PLD-0011)