Abstract
The UK’s Defence Science and Technology Laboratory (Dstl) is partnering with the US Naval Research Laboratory (NRL) on a joint mission to launch miniature sensors that will advance space weather measurement and modelling capabilities. The Coordinated Ionospheric Reconstruction Cubesat Experiment (CIRCE) comprises two 6U cube-satellites that will be launched into a near-polar low earth orbit (LEO), targeting 500 km altitude, in 2021. The UK contribution to CIRCE is the In situ and Remote Ionospheric Sensing (IRIS) suite, complementary to NRL sensors, and comprising three highly miniaturised payloads provided to Dstl by University College London (UCL), University of Bath, and University of Surrey/Surrey Satellite Technology Ltd (SSTL). One IRIS suite will be flown on each satellite, and incorporates an ion/neutral mass spectrometer, a tri-band global positioning system (GPS) receiver for ionospheric remote sensing, and a radiation environment monitor. From the US, NRL have provided two 1U Triple Tiny Ionospheric Photometers (Tri-TIPs) on each satellite (Nicholas et al., 2019), observing the ultraviolet 135.6 nm emission of atomic oxygen at night-time to characterize the two-dimensional distribution of electrons.
Highlights
The Coordinated Ionospheric Reconstruction Cubesat Experiment (CIRCE) will characterise a region of the space environment, the ionosphere, which is important for a range of defence and civil applications and can impact global navigation satellite system (GNSS), communications and sensing technology
CIRCE comprises two 6U1 (2U Â 3U) CubeSat buses provided by Blue Canyon Technologies, to fly a total of 10 payloads
As both satellites transition back towards the night-side, the trail satellite will rotate 180° once again. Both Ionospheric Sensing (IRIS) suites will continue to operate during transit of the night side. These regular manoeuvres mean that a few times a day, the TOPCAT II (GPS, see Sect. 4.2) and Triple Tiny Ionospheric Photometers (Tri-TIP) (UV optical, see Sect. 2.2) instruments both have the same point of view, enabling direct data comparisons
Summary
The Coordinated Ionospheric Reconstruction Cubesat Experiment (CIRCE) will characterise a region of the space environment, the ionosphere, which is important for a range of defence and civil applications and can impact global navigation satellite system (GNSS), communications and sensing technology. Nicholas et al (2019) provides an overview of the CIRCE mission. The phase and group delays, reflection, and refraction that the entire ionosphere produces (especially near the maximum ionisation region, within the F2 layer) can affect the propagation of radio signals across a significant proportion of the electromagnetic spectrum, including into the microwave region In addition to this background variability, space weather effects such as solar flares and coronal mass ejections The high frequency fadeouts discussed above, due to enhanced electron density in the D region, were found to occur in association with solar flares (Dellinger, 1937) These were later attributed primarily to X-ray emission from the flare, and are part of the category of sudden ionospheric disturbances. A single satellite in LEO has a ~90 min revisit period, a multi-satellite constellation would improve on this, but it is the dual-nature of the two relatively closely-spaced CIRCE satellites that is anticipated to provide unique insights into the temporal dynamics associated with specific ionospheric structures
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