SIGINT: The Mission CubeSats are Made For

The collection of radio frequency (RF) signals by means of interferometry is an area that shows great promise for small satellite applications and is a shared interest of business and the scientific and military community. SIGnals INTelligence or SIGINT is one of the oldest missions for satellites, especially for its subfield, ELectronic INTelligence (ELINT), the analysis and localization of RF-signals. Unfortunately, the accuracy that customers demand from such systems in order to merit their costs is often incongruent with detection techniques that rely on single nanosatellites (such as Angle of Arrival methods). Accuracy is strongly related to aperture size; rigid antennas are therefore limited to the available surface area of small satellites. Typical accuracies that can be expected of AOA-techniques range from 0.1° – 1°1. Factoring in orbital altitude, this results in geolocation accuracies of 10 km or more for RF-sources close to the satellite’s nadir, increasing rapidly with distance from nadir for missions in LEO. Using a single CubeSat solution with rigid antenna systems limits the type of RF-emitters that can be geolocated with high accuracy (\u3c 0.1°) to X-band (or shorter wavelengths). Deployable structures and small satellites that do not adhere to the CubeSat standard offer a limited solution as there is limited volume available for deployment mechanisms. One of the key benefits of using CubeSats is their lower unit and launch cost. This enables technical solutions that depend on distributing the desired functionality over many satellites, instead of investing in highly sophisticated single satellite payloads. This approach has in the past been studied for space-based interferometers like Orbiting Low Frequency Antennas for Radio Astronomy (OLFAR) enabling far larger diameter “apertures” than could be fitted on a single satellite while at the same time simplifying the development and deployment2. The same technologies that enable these scientific missions are at the heart of satellite formations for the purpose of identifying and geolocating RF-emitters on the Earth’s surface, such as inter-satellite datalinks, station-keeping systems and precise avionics. The overlap is not limited to these enabling technologies but also extends to system level characteristics. One of the big obstacles for CubeSat missions beyond LEO is their reliability. CubeSat missions beyond LEO face two hurdles that amplify each other, on the one hand the radiation environment becomes significantly more hostile, complicating the use of COTS components and on the other hand the cost of replenishment increases drastically with distance from Earth. Missions such as OLFAR thus require a step change in the reliability of the subsystems in order for them to be affordable and cost effective. At the same time these same reliability improvements would further decrease the cost of ownership of LEO spectrum monitoring (or SIGINT) constellations

Solving the Thermal Challenge in Power-Dense CubeSats with Water Heat Pipes

This paper describes the results of a project researching the application of water heat pipes in CubeSats. Heat pipes are proposed to solve for the increase in CubeSat power density, being one of the main thermal challenges appearing in high-performance missions. Commercial off the shelve water heat pipes have been tested and a proof-of-concept design has been made showing the flexibility of heat pipe integration. Thermal tests reflecting a common hot- and cold case experienced in low-Earth orbit, have been carried out. These tests have proven that the water heat pipe is capable of keeping a single component generating a continuous heat dissipation of 10W, within a reasonable temperature range and successfully start-up from a frozen state before temperature limits are breached. The outcome of this research has shown that water heat pipes can be the thermal solution for high performance CubeSat missions

Multi-Spectral Imaging from LEO: High-Resolution Images and Data from the NAPA-2 Turn-Key Mission

Napa-2 is a 6U Earth observation satellite flying the Simera Sense MultiScape 100CIS: a 7-band multi-spectral line-scan imager. Together with an on-ground calibration and processing chain from Pinkmatter Solutions, the Napa-2 system can deliver high-quality multi-spectral line scan images at an impressive ground sampling distance of 5m. After its launch and deployment in July 2021, hundreds of line scan images have been taken and valuable (and critical) data was obtained from the spacecraft platform related to attitude and control and timing. Imperative to the success of obtaining high-quality images, was the implementation of the newly developed ISISPACE Attitude Determination and Control System (ADCS). Line scan images were acquired under different conditions, such as simple flyovers, target pointing, and while executing forward-motion compensation maneuvers. The latter included imaging while the ground speed was reduced up to 50 times! In addition, time-delayed integration was applied in various levels to find the optimal signal-to-noise ratio. With the demand for hyper-spectral imaging from CubeSats, ISISPACE believes that the operational experience gained with multi-spectral imaging in combination with the attitude and orbital control system is vital to be able to educate future customers on the optical performance they can expect

Conquering the Solar System with CubeSat Technology – First Results of CubeSat Hardware Beyond Low Earth Orbit

This paper sets out to show the in-flight results of The Netherlands-China Low-Frequency Explorer (NCLE) – one of the first times CubeSat hardware has left low Earth Orbit. The Netherlands-China Low-Frequency Explorer (NCLE), is a low-frequency payload which is part of the Chinese Chang’e 4 mission. The NCLE instrument consists of three 5-meter long monopole antennas mounted on the Queqiao satellite and will be measuring in the 80 kHz - 80 MHz radio frequency range. The instrument is designed to address a multitude of high-profile science cases, but predominantly NCLE will open up the low-frequency regime for radio astronomy and will prepare for the ground-breaking observations of the 21-cm line emission from the Dark Ages and the Cosmic Dawn, considered to be the holy grail of cosmology. The design of the instrument began in May 2016, with a launch scheduled May 2018. This left only 2 years to develop, build and test the instrument. Given the short development time the design is based on COTS and space qualified components as much as possible, and a design and model philosophy common to nano-satellites was adopted. Even so, special care had to be taken as one of the main challenges of this mission is EMC. This is an area which is only marginally considered during a typical CubeSat project and required a different approach. Following the delivery in March 2018, less than 2 years after the project started, the instruments was successful launched in the 21st of May 2018 and saw its first return of telemetry January 2019. In this paper, the design of the instrument will be covered, as well as the first in flight results which were obtained. These results indicate NCLE is performing admirably after having spent over a year in interplanetary space. The NCLE instrument represents one of the first times the CubeSat methodology and hardware left Low Earth Orbit. This, together with the strict EMC requirements have resulted in CubeSat hardware which can be used in future interplanetary missions. The promising results give strong confidence in the technology and enables new mission opportunities which could not be served by CubeSats in the past. This will fuel the next phase of the CubeSat revolution where they will venture out into interplanetary space in support of bigger missions

Routine Health Outcome Measurement: Development, Design, and Implementation of the Hand and Wrist Cohort

Routine measurement of outcome of clinical care is increasingly considered important, but implementation in practice is challenging. This article describes (1) how the authors created and implemented a routine outcome measurement cohort of patients with hand and wrist conditions and (2) how these data are used to improve the quality of care and facilitate scientific research. Starting in 2011, routine outcome measurement was implemented at all practice sites (currently 22) of a specialized treatment center for hand and wrist conditions across The Netherlands. The authors developed five "measurement tracks," including measurements administered at predetermined time points covering all hand and wrist disorders and treatments. An online system automatically distributes measurements among patients, which can be accessed by health care professionals. Using this system, the total number of yearly assigned tracks increased up to over 16,500 in 2018, adding up to 85,000 tracks in 52,000 patients in total. All surgeons, therapists, and other staff have direct access to individual patient data and patients have access to their treatment information using a secure patient portal. The data serve as a basis for studies on, among others, comparative effectiveness, prediction modeling, and clinimetric analyses. In conclusion, the authors present the design and successful implementation of a routine outcome measurement system that was made feasible using a highly automated data collection infrastructure, tightly linked to the patient journey and the workflow of health care professionals. The system serves not only as a tool to improve care but also as a basis for scientific research studies

Getting the Bigger Picture: More Bytes for your Buck

UK-DMC-2 and Deimos-1 will be in orbit after a multi-satellite launch at the end of 2008 and will mark the start of the Next Generation Disaster Monitoring Constellation (DMC-NG). Whereas Deimos-1 is under contract for the Spanish company Deimos Imaging SL, UK-DMC-2 is SSTL’s own investment. This paper describes the UK-DMC- 2 and Deimos-1 missions and the technical design of UK-DMC-2, focussing on the latest developments and experimental subsystems such as an innovative GPS-receiver, enhanced sun-sensors and a set of COTS heat pipes. New operational modes such as near real time imaging and downlink and a direct broadcast mode to multiple ground stations provides a substitute service for customers currently receiving Landsat data. Due to UK-DMC-2’s high throughput potential, it will be used to assist in large area coverage campaigns

Synthesis and biological evaluation of (11)C-labeled beta-galactosyl triazoles as potential PET tracers for in vivo LacZ reporter gene imaging

In our aim to develop LacZ reporter probes with a good retention in LacZ expressing cells, we report the synthesis and preliminary evaluation of two carbon-11 labeled beta-galactosyl triazoles 1-(beta-d-galactopyranosyl)-4-(p-[(11)C]methoxyphenyl)-1,2,3-triazole ([(11)C]-6) and 1-(beta-d-galactopyranosyl)-4-(6-[(11)C]methoxynaphthyl)-1,2,3-triazole ([(11)C]-13). The precursors for the radiolabeling and the non-radioactive analogues (6 and 13) were synthesized using straightforward 'click' chemistry. In vitro incubation experiments of 6 with beta-galactosidase in the presence of o-nitrophenyl beta-d-galactopyranoside (ONPG) showed that the triazolic compound was an inhibitor of beta-galactosidase activity. Radiolabeling of both precursors was performed using [(11)C]methyl iodide as alkylating agent at 70 degrees C in DMF in the presence of a small amount of base. The logP values were -0.1 and 1.4, respectively, for [(11)C]-6 and [(11)C]-13, the latter therefore being a good candidate for increased cellular uptake via passive diffusion. Biodistribution studies in normal mice showed a good clearance from blood for both tracers. [(11)C]-6 was mainly cleared via the renal pathway, while the more lipophilic [(11)C]-13 was excreted almost exclusively via the hepatobiliary system. Despite the lipophilicity of [(11)C]-13, no brain uptake was observed. Reversed phase HPLC analysis of murine plasma and urine revealed high in vivo stability for both tracers. In vitro evaluation in HEK-293T cells showed an increased cell uptake for the more lipophilic [(11)C]-13, however, there was no statistically higher uptake in LacZ expressing cells compared to control cells.status: publishe

Synthesis and preliminary evaluation of 18F- or 11C-labeled bicyclic nucleoside analogues as potential probes for imaging varicella-zoster virus thymidine kinase gene expression using positron emission tomography

Two radiolabeled bicyclic nucleoside analogues (BCNAs) were synthesized, namely 3-(2'-deoxy-beta-d-ribofuranosyl)-6-(3-[18F]fluoroethoxyphenyl)-2,3-dihydrofuro[2,3-d]pyrimidin-2-one ([18F]-2) and 3-(2'-deoxy-beta-d-ribofuranosyl)-6-(3-[11C]methoxyphenyl)-2,3-dihydrofuro[2,3-d]pyrimidin-2-one ([11C]-3), and evaluated as PET reporter probes for varicella-zoster virus thymidine kinase (VZV-tk) gene expression imaging in brain. [18F]-2 and [11C]-3 were synthesized starting from phenol precursor 1. The phenol precursor 1 was converted to stable as well as to radiolabeled compounds 2 and 3 using (19/18)FCH(2)CH(2)Br or (12/11)CH(3)I as alkylating agent. In vitro evaluation of [18F]-2 and [11C]-3 in 293T cells showed a 4.5 and 53-fold higher uptake, respectively, into VZV-tk gene-transduced cells compared to control cells. However, biodistribution studies in mice demonstrated low uptake of these tracers in the brain. RP-HPLC analysis of plasma and urine samples of mice injected with [11C]-3 revealed that this tracer is very stable in vivo. These data warrant further evaluation of these tracers as noninvasive imaging agents for VZV infection and VZV-tk reporter gene expression in vivo.status: publishe