DANDE was elected as an entrant to the University Nanosat Program competition, a two year program that is now in its eighth iteration. In 2009, DANDE won additional funding and a future flight to orbit. The DANDE satellite is the first CU student-built satellite launch opportunity in five years. To date, about 100 students have been involved in DANDE through construction, testing, and operations.
DANDE’s mission statement is to explore the spatial and temporal variability of the neutral thermosphere at altitudes between 200 and 350 km (revised to 325-500 km due to being assigned to a new orbit since the beginning of the project), and investigate how wind and density variability translate to drag forces on satellites. The density of the atmosphere varies greatly due to space weather and other unknown processes. The International Space Station once dropped in height by tens of kilometers in a span of a few days - and by understanding drag forces and composition of the atmosphere we can provide better data about this phenomenon.
In the diagram below, items in green can be found using on board instruments. Blue are prior (a priori) knowledge, and red are variables that can be solved for.
ACC (Accelerometers) - DANDE’s ACC system is one of the two science subsystems on the satellite. Its purpose is to measure DANDE’s acceleration along its orbit. Using the acceleration data, coupled with density data acquired from NMS, the drag on DANDE can be calculated.
ADC (Attitude Determination and Control) - DANDE’s Attitude Determination and Control (ADC) subsystem serves to create a certain spin rate (in revolutions per minute) of DANDE, and make adjustments to align DANDE in a certain way relative to the Earth. The ADC subsystem utilizes Magnetometers, Magnetic Torque Rods, and Horizon Crossing Indicators (HCI’s) to determine DANDE’s alignment and spin rate. There is also a nutation damper system allowing for passive attitude determination on DANDE. This subsystem uses the data gathered from these components to send commands to DANDE that will align and spin DANDE in a predetermined way for the purposes of this mission.
CDH (Command and Data Handling) - Written in the programming language C and running under a Linux operating system, the main goals of CDH are to 1) Execute commands received from the ground 2) collect and store engineering data 3) collect and store science data (NMS and ACC) and 4) monitor the satellite's processes and subsystem critical thresholds.
COM (Communications) - DANDE uses a full-duplex communications architecture which allows uplinking and downlinking commanding to operate on two separate frequencies.
EPS (Electrical Power System) - EPS includes the solar array located on the hemispheres, twenty Ni-Cd batteries, and a peak power tracker that monitors and adjusts the charging limits based on temperature in order to maximize power output.
NMS (Neutral Mass Spectrometer) - Comprised of four chambers, NMS takes neutral atoms from the atmosphere and outputs atmospheric density data in conjunction with data from ACC to calculate the drag on DANDE.
SEP (Separation Subsystem) - The separation subsystem’s main task is to eject DANDE from the LightBand Adaptor Bracket, or LAB, that attaches DANDE to the launch vehicle. This phase of the mission occurs after DANDE has been jettisoned from the launch vehicle and has been powered on to a nominal state.
THM (Thermal Subsystem) - DANDE’s Thermal Subsystem monitors the temperatures of all components that make up the satellite. The system can be broken into two sections, internal and external. Internally, we have sensors on every subsystem with multiple nodes on each to be able to monitor temperature changes across each subsystem. Externally, we have the solar cells, shell, and equatorial plate that are monitored. The range of temperatures we expect to see while in orbit may range from 10-30 degrees Celsius, but our operating temperature limits can drop to 0 degrees Celsius or be as high as 50 degrees Celsius.
The DANDE Mission Operations team has broken down DANDE’s on-orbit mission lifetime through a series of phases and mode functions. Within each phase, multiple mode changes will occur. Before the next phase of DANDE’s mission can begin, the success criteria for the previous phase must be verified through data that was downlinked. The four phases are as follows:
Activation Phase - Primary goal: Ensure initial operable functionality state of DANDE.
Separation Phase - Primary goal: Separating DANDE from the LAB (Lightband Adapter Bracket)
Spin Up/Attitude Phase - Primary goal: DANDE spinning at a rate between 9-11 RPM parallel to its orbital velocity vector, and to aligh the spin axis with the angular momentum vector of the orbital plane within 2 degrees.
Science Commissioning Phase - Primary goal: To initiate the NMS and ACC instruments to acquire NMS and ACC data.
Pictured below is the DANDE spacecraft as of August, 2008 - current configuration to date.