AFSPC-05 Secondary Payloads - Spaceflight101

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AFSPC-05 Secondary Payloads
X-37B Updates, LightSail-A, USS Langley, AeroCube-8A/B, BricSat-P, PSAT-A, OptiCube, GEARRS-2

Being launched as a secondary payload aboard the Atlas V 501 rocket carrying the X-37B OTV-4 spacecraft is the UltraSat CubeSat (Ultra Lightweight Technology and Research Auxiliary Satellite) Deployer that hosts eight Poly Picosatellite Orbital Deployers, each capable of facilitating three CubeSat Units (either as a single 3U CubeSat or multiple smaller satellites). A complete list of satellites that are being launched aboard UltraSat has been published by United Launch Alliance, details on all satellites known to be part of this launch can be found below.

Image: NRO

Image: United Launch Alliance

LightSail-A

Image: The Planetary Society

LightSail-A is a 3-Unit CubeSat developed and operated by The Planetary Society to demonstrate sunlight, or rather solar pressure, as a means of spacecraft propulsion for potential future use in large sails for deep space propulsion.

The LightSail-A mission will only function as a demonstration of the mechanical systems used in the deployment of the sail and validate the satellite bus for a longer test mission in a higher orbit in 2016 to actually demonstrate spacecraft acceleration through solar pressure.

>>>Detailed Spacecraft Overview

USS Langley

The Unix-Space-Server Langley is a three-Unit CubeSat built and operated by the U.S. Naval Academy. It is part of a concept study looking at the feasibility of deploying a constellation of small low-cost satellites to orbit capable of TCP/IP based communications to act as Internet servers in space to provide a faster link between clients and hosts without the need for a terrestrial network.

The USS Langley development team consists of undergrad students and two professors at US Naval Lab. USS Langley also continues the study of the PSK-31 multi-user transponder and its application in future space projects.

The USS Langley satellite uses a 3-Unit CubeSat bus procured from Pumpkin Inc. under the Colony-1 program of the National Reconnaissance Office.

Image: Naval Research Lab

The bus facilitates all satellite support systems including the Electrical Power System that hosts 43 solar cells installed on 7 panels – four deployable solar panels each measuring 10 x 30 centimeters and three of the satellite side panels. Power is stored in a 20-Watt-hour battery and dedicated avionics are controlling the state of charge of the battery and conditioning the 8.3, 5 and 3.3-Volt power buses. The satellite uses a fully operational Attitude Determination and Control System with magnetometers, magnetic torquers, inertial measurement units and reaction wheels.

BeagleBoard

Image: Beagleboard, NRL

HD Camera

USS Ground Terminal Connections

Photo: Beagleboard, ClydeSpace, NRL

The USS Langley satellite will act as a webserver and router in space using standard Internet Protocol (IP) and operating on the Linux operating system. The use of IP in space was first envisioned by NASA, but since its use in higher orbits is impractical, the idea was abandoned. Linux is also rarely used in satellite applications, and has never been employed as a space-based webserver.

The main payload of USS Langley is a BeagleBoard-xM open-source computer powered by a TI Sitara processor that has been chosen due to its compact form factor and customizability. The satellite uses a 1GHz processor and 512MB of RAM memory plus a 32GB flash drive to store payload data. A dedicated module facilitates an HD camera that acquires photos of Earth that are then sent to the flash memory and placed on the website hosted by the webserver.

The USS Langley satellite uses a 2.4GHz S-Band system for communications between itself and Remote Internet Users employing a 128-bit AES encryption and operating at a data rate of 935Kbps. The AW2400 AvaLan Wireless system has a transmit power of 1.7 Watts and a nominal receive power of 0.8 Watts. Command and Data Handling is accomplished in UHF using a standard communications terminal operating at the 435MHz frequency. Satellite management and Command and Data Handling is accomplished with an Arduino Pro processing system and a ArduIMU for GPS, Accelerometer, Magnetometer and Gyrometer operation. The satellite will provide webserver access to a ground station in Annapolis and other stations so that remote users can also access the website generated onboard the satellite via the terrestrial network.

USS Langley also continues the in-space evaluation of the PSK31 Linear Transponder that operates in the VHF range for uplink at 145MHz and UHF for downlink at 437MHz. The transponder can be used by up to 20 amateur radio operators at a time to relay radio packets as short messages.

AeroCube 8A & 8B

Aerocube 8 is part of the small satellite program of The Aerospace Corporation, El Segundo, California. The AeroCube program deploys small satellites for technical demonstrations. Each of the two AeroCube 8 satellites is 1.5 Units in size and hosts a new electric propulsion system, new nanotechnologies and new innovative solar cell technologies that are to be tested in an operational space environment.

The AeroCube 8 satellites demonstrate a Scalable ion-Electrospray Propulsion System (SiEPro) that is based on the extraction and acceleration of heavy ions using strong electric fields applied at the interface between the propellant and the vacuum of space. The system uses field evaporation to generate charged particles which has the advantage of not needing any reaction volume for the production of ions. Typical ion thrusters require a reaction chamber into which a molecular gaseous substance is injected to then be ionized by electron bombardment or other methods. Additionally, the propellant, held by a porous substrate and guided through planar emitters, does not need to be pressurized and flows exclusively by capillarity forces. Eliminating propellant lines, valves, tanks and pressurization complies with the size and weight limitations of CubeSat designs.

Image: Aerospace Corporation

Typically, the propellant used by the system is a liquid-salt that is non-toxic and held inside a plastic tank as main propellant reservoir. Atop the tank is a porous material that guides the fluid to a few hundred pointed tips made of metal. Flow of the propellant through the porous material is accomplished through the use of capillary forces.

The porous material holding the propellant is comprised of silicon with micro-fabricated porous metal substrates that contains the ion emitting structures. Located above the ion emitting structures is the extraction grid that is biased at voltages of up to 1000 Volts to extract the ions from the ion emitting structures and provide initial ion acceleration.

Image: Space Propulsion Laboratory/Dan Courtney

An optional pair of accelerator grids can be installed atop the extractor to further accelerate the ions. As the high-speed heavy ions are ejected, the spacecraft is accelerated in the opposite direction according to Newton’s third law. Overall, the thruster module is about 10 by 10 by 2.5 millimeters in size.

A total of four SiEPro modules would be needed in a minimum configuration for CubeSat attitude control and main propulsion. SiEPro can also be used for CubeSat Deorbit maneuvers, formation flying and missions beyond Earth orbit. Typical 3U CubeSats would feature 32 SiEPro modules for attitude control and main propulsion.

The AeroCube 8A and 8B satellites also demonstrate the use of a light-weight harness and the use by Carbon Nanotube radiation shielding for application in future satellites. In addition, the satellites demonstrate the use of quadruple-junction inverted metamorphic multi-junction (IMM) solar cells and quintuple-junction Semiconductor Bonding Technology (SBT) solar cells.

BRICSat-P

BRICSat-P, known also by its full name Ballistic Reinforced Communication Satellite, is an experimental satellite mission operated by the US Naval Academy Satellite Lab to demonstrate the on-orbit operation of a Micro-Cathode Arc Thruster (µCAT). The satellite also carries on Amateur Communications Payload to be accessed by radio operators around the world. The satellite is 1.5U in size and weighs 1.9 Kilograms.

µCAT aims to create a small-satellite propulsion system that uses low-cost components, eliminates the use of pressurized systems, operates with low-power, is scalable and modular, and is safe for the satellite. The µCAT system consists of several Thruster Heads – each consisting of two coaxial electrodes that are separated by several millimeters of Electric Solid Propellant with a Magnetic Coil on the forward end of the thruster. Each thruster head measures one centimeter in diameter and 2.29 centimeters in length.

The Anode is located in the center of the thruster while the titanium Cathode material builds the external shell of the thruster. The solid propellant used in these thrusters can only ignite when an electric current is applied and only sustain operation as long as the current is present. This allows for precise control and a reliable ignition.

Conventional solid-fueled thrusters can not be controlled – once ignited, they burn until expending all their propellant. Thrust on the µCAT is generated through outstreaming electrons and atoms. These types of thrusters are an interesting alternative because they require no moving parts and their propellants are extremely safe as they are insensitive to flames or electrical sparks.

Propulsion Board

The µCAT thrusters operate at frequencies between one and 20 Hz, generating impulse bits of 1mNs per pulse and operate at a specific impulse of 2000 to 3000 seconds, much higher than conventional liquid-fueled thruster systems. The mass of the system with its individual thrusters and the central Propulsion Power Unit is around 200 grams. Overall, for a 4kg satellite, the system can deliver a delta-v of 300m/s.

BRICSat-P uses four thruster heads that are arranged around the center of mass of the spacecraft. The µCAT thruster system will be used for the initial de-tumble of the CubeSat, the control of an initial spin around two satellite axes, precise attitude hold control and operation in delta-v mode. Gyroscopes will be used to measure the performance of the propulsion system.

The de-tumble experiment is expected to take seven orbits before the satellite enters a stable attitude with a target stability of under one degree per second. The rotational experiment will operate the thrusters at a 22% duty cycle to spin up to 6RPM with the satellite cameras acquiring photos of the operation of the thrusters.

For a delta-v maneuver, the four thrusters will be fired along the magnetic field line of Earth, measured by the vehicle’s magnetometers.

BRICSat-P also carries two amateur communication payloads – an Automatic Packet Reporting System (APRS) Transponder with downlink at 437 MHZ and uplink at 145 MHz, and a PSK31 Transponder with a 28MHz uplink and standard UHF downlink.

PSAT-A

The PSAT Project (ParkinsonSAT) has been developed by students at the US Naval Academy Satellite Lab as a two-way communications transponder system that could be used to relay data from remote terminals to a global network of internet linked volunteer ground stations to speed up the return of data from remote environmental sensors, and other experiments that are installed in remote locations to the operators of the experiments.

Each PSAT is based on the 1.5U form factor using solar cells for power generation and a 10-Watt-hour battery plus passive magnetic torquer attitude control. The solar cells are installed on body-mounted solar panels that are oriented towards the sun by the satellite’s attitude control system using a passive mechanism consisting of a highly reflective strip on the clockwise edge so that the satellite enters a slight spin around the z-axis to ensure even charge of the battery strings from each of the four solar panels. A single magnetic torquer on the z-axis of the satellite allows the spacecraft to be aligned with Earth’s magnetic field to keep the side panels within a +/-23-degree corridor to the sun.

The two PSAT satellites host a AX.25 Packet Radio Relay system based on the Automatic Packet Reporting System which has been used in previous CubeSat applications and demonstrated the distribution of data packets to users worldwide via the global network of volunteer ground stations feeding data straight to the Internet. Additionally, the PSAT spacecraft are equipped with a PSK31 transponder that allows multi-user access to the satellite. This text messaging transponder can allow messaging between 30 ground stations simultaneously. The systems operate using the standard VHF (145MHz) and UHF (437MHz) frequencies for up and downlink.

Optical CubeSats

Three Optical CubeSats, also known as O/C-1,2,3 or OptiCube, are part of the AFSPC-05 launch. The project is sponsored through a contract by the National Reconnaissance Office and the satellites were developed and manufactured by CalPoly (PolySat). Each of the satellites uses the 3U form factor to provide small orbital targets that can be used to test orbital debris tracking technologies to improve small-object tracking in Low Earth Orbit. Current sensors can track small object with a side of ten centimeters, however, tracking of small objects becomes more difficult at lower altitudes which can have implications on Low Earth Orbit spacecraft including the International Space Station.

GEARRS-2

GEARRS-2 is the second Globalstar Experiment And Risk Reduction Satellite, launched in a project operated by NearSpace Launch to investigate the use of the Globalstar satellite communications network for the command and control of a small satellite systems and CubeSats flown to Low Earth Orbit. The project finds its heritage in technology developed at Taylor University and the TSAT experiment flown in 2014. The first GEARRS satellite was deployed from the International Space Station in March 2015 after being launched by the Cygnus Orb-2 mission in July 2014.

The use of Globalstar for controlling small satellites would enable 24/7 access to the spacecraft instead of the usual ground-station communication passes that can last from a few minutes per day to a few hours, depending how many Stations are being used for a particular mission. Globalstar is a satellite constellation operated in a 1,420-Kilometer orbit to deliver low-latency low-data rate communications such as voice and data connectivity between two ground terminals including mobile users.

The 3U CubeSat will test communication links through the GlobalStar network to confirm the capability of operating microsatellite systems through low-cost access via GlobalStar for science and commercial objectives.