To study space weather, which includes 

• magnetic field line currents, 
• radiation in space,
• Ionospheric electron density and temperature

To collect data pertaining to 

• wildfire prediction, 
• identification,
• post-burn effects for at-risk regions around the world.

Ex-Alta 1 had four payloads:

1. Multi Needle Langmuir Probe (MNLP): A probe to study space weather by precisely measuring electron density and temperature in the ionosphere.
2. The Digital Fluxgate Magnetometer (DFGM) which measured magnetic signatures in space weather
3. A radiation dosimeter which routinely monitored radiation of the spacecraft
4. Athena: an open-source on-board computer made by UAlberta students flying for the first time on this mission.

Ex-Alta 2 has two payloads:

1. Iris : An in-house multispectral imager (a camera-like instrument) to capture spectral data of both ground vegetation and the atmosphere that allows scientists to make observations about wildfires.
2. The Digital Fluxgate Magnetometer (DFGM) which measures magnetic signatures in space weather

The importance of studying space weather

Space weather affects the health of satellites in orbit, radiation exposure of personnel in airplanes, power infrastructure on Earth, and life on Earth in general.

Objective:

To obtain data that will further our understanding of space weather, ultimately helping us predict and prepare.

The importance of studying wildfires

Wildfires lead to burning of millions of acres of land across the world every year. For example, about 4.7 million acres were burned in the year 2019 alone. This dramatically affects many communities across the world. 

Additionally, rising global temperatures are leading to an increase in the number and intensity of wildfires every year.

Objective:

The data collected will help us better understand the start and spread of wildfires so we can better prevent disasters like the one Albertans saw in Fort McMurray in 2016.

Ex-Alta 1’s scientific mission was to study space weather using a Digital Fluxgate Magnetometer with the  notion of how it can severely impact Earth’s magnetic field. Relative to Earth, space weather refers to changes in the space environment dependent on solar activity.The following image by the European Space Agency provides a visual  summary of how changes in solar activity can affect us.

The sun’s magnetic field goes through a cycle (solar cycle) in which it flips on itself every 11 years. The activity varies from cycle to cycle, but the probability of geomagnetic storms occur near the peaks of the cycle . According to NASA, since December 2019 we are currently in cycle 25 with another  solar maximum predicted to be in year 2025. The image below shows the sun during solar maximum(left, April 2014) and solar minimum(right, December 2019) during our current cycle.

Ex-Alta 2’s Inclusion of the in house Iris pushbroom style multispectral imager will enable us to  analyze spectral bands required to calculate multiple spectral indices, for example normalized difference vegetation index (NDVI) and normalized burn ratio (NBR). These indexes play an important role in creating accurate fire severity assessments for prevention and prediction.

NDVI: Normalized difference vegetation index is calculated using the visible and near infrared light that is reflected by vegetation. Usually healthy vegetation absorbs quite a lot of visible light leaving a strong NIR (Near Infrared) reflectance signature [Ceccato et al., 2002]. Following this logic, areas with a lesser density/unhealthy vegetation give a stronger visible light (red/green/blue) reflectance signature. Processing data using the formula presented below  gives an output of either -1 or +1. Areas of dense vegetation will have values close to +1 while  a lack or absence of vegetation will be close to zero. Ex-Alta 2 will be using bands of 620-670nm  and 840-880nm to determine NDVI ratios.

NBR: Normalized Burn Ratio uses the calculated ratios of short wave Infrared (SWIR)reflectance and near infrared (NIR) reflectance to identify burned areas and quantify the burn severity.SWIR helps identify changes in water content and soil exposure [Jensen, 2000; Lillesand and Kiefer, 2000] while NIR is sensitive to the vegetation density/biomass [Ceccato et al., 2002],

With this information we can eventually calculate a normalized dynamic  burn severity of the landscape by subtracting the pre-fire ratio from the post-fire ratio [Key and Benson, 1999, 2005],

• 3U CubeSat structure manufactured by Innovative Solutions In Space (ISISpace)
• Size (cm) : 34 x 10 x 10
• Weight of the structure: 0.304 kg
• Weight of the satellite: 2.64 kg
• Structure is made of aluminum 6082

• 3U CubeSat structure named Icarus is manufactured in-house (designed and built by students at the UofA)
• Size (cm) : 34 x 10 x 10
• Expected Weight of the structure: 0.306 kg
• Expected Weight of the satellite: 4.16 kg
• Icarus is made of aluminum 6061 T6

GomSpace P31uS NanoPower electrical power system (EPS)

Battery:  

• Battery Pack (GomSpace BP4) is composed of 4 Lithium Ion (Li-ion) 18650 space proven batteries in a 4 series 1 parallel (4S1P) formation
• Total battery energy: 37.44 watt-hours (Wh)

Solar Panels: 

• Integrated solar panels 
• Two series-connected AzurSpace 3G30A space qualified triple junction solar cells per solar panel
• Efficiency of solar cells: 30% 
• The solar panels covered every outward facing side of the satellite except the side to which the MNLP is attached and the center face of the side from which the DFGM boom deploys.

NanoAvionics Electrical Power System “EPS”

Battery:

• On-board two Lithium-Ion batteries in 2S1P and 2S7P battery configuration with integrated Battery Management System (BMS)
• Capable of supporting external battery packs with different configurations, such as standard PC/104 configuration as well as with custom mechanical layout, up to 2S7P configuration.
• Total battery energy: 161 watt-hours (Wh)

Solar Panels: 

• Solar panels are being designed and built in-house by undergraduate volunteers
• Deployable solar panels are included for extra power generation
• Spectrolab XTJ prime cells in parallel strings of 2 cells in series per solar panel
• Efficiency of solar cells: 30.7% 

OBC for Ex-Alta 1: 

• NanoMind A721D

• Uses an ARM7 processor with two I2C busses, one 4Mbyte Data Flash and a 2 GByte SD Card. 

• A dedicated board named the NanoHub was connected to the Flight Preparation Panel (FPP) and is burn wire release controller for the satellite.

• NanoHub is both an interface and a utility system. It provides a number of necessary interfaces for the seamless integration of a satellite.

• It integrates ground support interfaces like USB to subsystem serial ports and Flight Preparation Panel connector together with inter-subsystem interfaces like digital IO, ADC and SPI and utilities like electrical knives, power switches, and gyros into one compact package.

OBCs for Ex-Alta 2:

Athena:

• Based on ARM Cortex R5F 
• 512MB of image data
• 215MB of DFGM data
• -40 to +65 celsius operating temperatures
• 32GB SD card
• Athena is responsible for data handling as well

COTS OBCs: Backup system

• Kryten
• OBC-II
• A3200-DMC3

The 3 OBCs listed above are being considered alongside Athena as the OBC put into Ex-Alta 2.

Surrey Space provided the CubeSpace Y-momentum ADCS. It controlled the orientation of the satellite using three magnetic coils and one weighted reaction wheel. 

It consisted of:

• pair of complementary metal oxide semiconductor (CMOS) cameras operating as Sun/Nadir sensors
• rate gyros,
• coarse photodiode sun sensors
• A magnetometer to determine the spacecraft’s relative orientation in its orbit.
• A single reaction wheel, acting as a momentum wheel,
• Three magnetorquers oriented in three orthogonal directions aligned with the CubeSat reference frame.

GPS:

• A Novatel OEM615 GPS and receiver module with H-code firmware was used in conjunction with the CubeSpace ADCS Module.
• Taoglas AP10.F GPS antenna consists of a 10×10 mm ceramic patch and was mounted to the zenith face of the satellite, on an interstage panel.

Ex-Alta 2 will use the CubeSpace 3 Axis ADCS which consists of:

• A deployable magnetometer
• Ten Coarse sun sensors (each with 1 harness)
• Two CubeSense units
• Three CubeWheels
• A CubeConnect

Ex-Alta 2’s GPS isn’t interfaced through the ADCS

GPS:

The GPS system integrated with Ex-Alta 2 will be made up of two components

• GPS Receiver: The SkyTraq S1216F8
• GPS Antenna: The Molex RHCP Ceramic GPS Antenna (146168)

• Purpose: make low-noise measurements of the magnetic signatures of space weather current systems
• Sensitivity: 1 nT
• Mounted on a deployable coil boom 
• Power: 50 mA at 5V (~250 mW)
• Sensor Dimensions: 20 x 20 x 40 mm 
• Sensor Mass: 100g 
• Electronics package volume: 90x96x15 mm
• Electronics package mass: 90g
• Survival Temperatures:
  • Sensor: -40 to +85C
  • Electronic: -40 to +85C
• Operating Temperatures:
  • Sensor: -40 to +85C
  • Electronic: -40 to +85C 

Magnetometer boom:

• German Aerospace Center (DLR) Solar Sail Boom was used.
• The boom is made up of a carbon fiber weave which allows for a great deal of strength for a low amount of mass (18 g/m).
• The boom length is 1 meter at a maximum.
• The boom is stored within the middle cube unit of the satellite.

• In-house Magnetometer
• Purpose: demonstrate the feasibility of studying small scale (~1 – 10 km) Field Aligned Currents (FACs) from a nanosatellite platform.
• Average DFGM collection duration: DFGM will produce 1256 bytes per second during operations. The OBC will be able to store 1.5 GB of DFGM data (equivalent to two weeks of continuous data). 
• DFGM Boom Elbow Importance: The DFGM boom has a large effect on the spacecraft’s moments of inertia (MOIs). If the DFGM sensor head’s deployed position is off-center, towards the port or starboard sides of the spacecraft, then the major principal axis of inertia will be misaligned with the satellite’s geometric Y-axis. For proper spacecraft stability, these axes need to be aligned. To resolve this, the DFGM boom may be designed so that the DFGM sensor head deploys such that it is a well-centered port-to-starboard as shown in the figure of Dog Leg angle.

Payload: Multi Needle Langmuir Probe (MNLP) 

Purpose

• High time resolution measurements of absolute electron density and spacecraft floating potential
• Study the effects of re-entry

Specifications

• Current range: 3 decades (i.e. 1 nA to 1 µA)
• Electron density range: 108m-3 to 1012m-3 
• Sampling rate: up to 10 kHz
• No voltage sweeping – Fixed bias voltage on all probes
• Developed by the University of Oslo
• The MNLP will be attached to the top face of the satellite and deploy using torsion springs

MNLP boom system:

• 4 separate booms mounted on the common top plate of the STS
• Each of the booms has an individual deployment mechanism, operated by the MNLP printed circuit board (PCB) on command from the OBC

MNLP electron emitter:

• implemented in the centre of the MNLP boom system
• Purpose: gets rid of collected electrons that drive the CubeSat floating potential below functional limits when the satellite is in eclipse where photoelectron emission is not possible
• emission currents as high as 20 μA 🡪 5 times higher than the maximum amount of collected current by positively biased MNLP probes

Payload: Iris Imager

• In-house Imager: Ex-Alta 2 shall produce an image that allows scientists to make observations about wildfires.
• Average Imaging Time: Per system requirements ASX2-PAY-2.010 and ASX2-SYS-5.060, the OBC must be able to store 512 MB of image data. This is equivalent to 4 days worth of imaging (six images), which will be deleted after downlinking the data.

Parameters of image data

Specifications:

• Signal to noise ratio of at least 20dB
• Occupy a volume of less than 1U (10cm x 10cm x 10cm)
• Spatial ground resolution of no more than 300m
• Spectral bands in use to capture relevant data:
  • 440-480nm
  • 620-670nm
  • 840-880nm
  • 2100-2160nm 
• Two apertures:
  • 30mm (visual-near infrared) approx. 122m resolution
  • 40mm (short wave infrared) approx. 205m resolution

Communication between Ex-Alta 1 and Ground Station was only via Ultra High Frequency (UHF) Band

UHF Band: 

• NanoCom U482C Half duplex Ultra High Frequency (UHF) transceiver and ANT430 turnstile UHF deployable antennas
• Outputting ~1.0 W radiated power
• Transceiver supports up to 9600 baud, with Consultative Committee for Space Data Systems (CCSDS) framing and forward error correction (FEC).
• Antenna is a four-rod omnidirectional turnstile antenna that is secured with burn wire against Ex-Alta 1 prior to deployment and deploys via torsion springs.
• Ground Station for UHF Band are in the UofA
• On Ex-Alta 1 most of the UHF Ground Station passes required human involvement.
• Transmit Frequency: 436.705 MHz  

Communication between Ex-Alta 2 and Ground Station is via Ultra High Frequency (UHF) and S-Band

UHF Band: 

• The UHF band will be prioritized for satellite health and maintenance, in-orbit activities (flight schedules), outreach games/data, Whole Earth Data (WOD) and addressing anomalies (if needed).

• Both uplink and downlink between the satellite and the ground station will be possible.
• Ground Stations for UHF Band are at the UofA
• Satellite operations will typically involve operation of the ground station, flight schedule creation and maintenance, addressing anomalies, and documentation of pass data and events.
• Transmit frequency: 435 – 438 MHz
• Data rate: 9.6 kbps 
• Average link time per day for UHF ground station = 35 mins/day.

S-band: 

• The S-band will be prioritized for payload (Iris and DFGM) downlink. 
• There will be no S-band uplink capabilities for Ex-Alta 2.
• Ground Stations for S-Band are in Prince Albert and Gatineau. Since there is no S-Band uplink, all downlinks over Natural Resource Canada S-band Ground Stations in Prince Albert and Gatineau will be programmed into the satellites flight schedules.
• S-band passes will be fully automated on the satellite during the Nominal Operations Phase.
• Transmit frequency: 2.4 GHz 
• Data rate: 10 mbps
• Average link time per day for both S-band ground stations:
  • Gatineau = 112.91 s/day
  • Prince Albert = 112.54 s/day
• S-band transmitter and antenna from Clyde Space

Orbited the Earth at an altitude of 415 km for up to 18 months before burning up during re-entry.

Launched to the International Space Station (ISS) April 18, 2017 from Cape Canaveral Air Force Station and was deployed from ISS on May 26, 2017. Its work ended on November 14, 2018. 

Averaged 4 to 5 passes over Edmonton per day. 

Set to orbit the Earth at a maximum altitude of 410 km for 1-2 years.

Currently in the works and set to launch in March 2022.

Based on Satellite Tool Kit (STK) simulations, there will be 5 passes a day (only for the case of UHF passes).