Science
Drag induced by the neutral-atmosphere density is the major perturbation on satellites in low earth orbit. True density deviates as much as 21% from model predictions, introducing error into crucial government and private space operations with applications to situational awareness, space surveillance, laser communications, re-entry prediction, rendezvous and proximity ops. A need exists to measure physical or 'true' density, quantify density variations, and to provide in-situ model calibration data.
The operating principle is to solve the full drag equation:
Each variable is isolated either by an a priori knowledge or via in-situ measurement. The mass (m) and area (A) are based on the physical parameters that can be measured prior to launch. The Coefficient of Drag is simulated using the external geometry of the spacecraft in its science collection state. Density (ρ), Acceleration (a), and a Wind Vector are sensed by two onboard instruments, the first is a high precision Accelerometer suite (ACC) that amplifies the μg drag signal in the along track axis of the spacecraft. Secondary to that is a Neutral Mass Spectrometer (NMS) that can provide data products relating the wind vector with respect to the spacecraft ram-vector as well as the numerical density of the constituents in the atmosphere. The idea is that at orbital velocities the spacecraft traveling through even a stagnant atmosphere will have collisions with the species present at energies of several Electron-Volts (eV) of which there are still billions per cubic meter.
DANDE is spherical in nature so the projected cross-sectional area is held nearly constant. This leverages a simplified attitude subsystem design as opposed to a full three-axis stabilized system. Further spinning about orbit normal allows the accelerometer instrument, located so the spin-axis is perpendicular to the acceleration sense axis, to accept in a modulated acceleration profile.
There were issues that make having GPS onboard the spacecraft prohibitive. As a student program the cost of an unlock GPS receiver that could provide data products in orbital scenarios was a chief concern, but the spacecraft attitude state would not be conducive to consistently providing a lock at all times when geolocating data. High Task Tracking is a possibility through Air Force Space Command Research and Analysis group, but that agreement does not solve all the needs at the beginning of the mission when the desire is to make contact and begin commissioning.
Read more about this topic: Drag And Atmospheric Neutral Density Explorer
Famous quotes containing the word science:
“Every known fact in natural science was divined by the presentiment of somebody, before it was actually verified.”
—Ralph Waldo Emerson (1803–1882)
“Science is the language of the temporal world; love is that of the spiritual world. Man, indeed, describes more than he explains; while the angelic spirit sees and understands. Science saddens man; love enraptures the angel; science is still seeking, love has found. Man judges of nature in relation to itself; the angelic spirit judges of it in relation to heaven. In short to the spirits everything speaks.”
—Honoré De Balzac (1799–1850)
“Thinking is seeing.... Every human science is based on deduction, which is a slow process of seeing by which we work up from the effect to the cause; or, in a wider sense, all poetry like every work of art proceeds from a swift vision of things.”
—Honoré De Balzac (1799–1850)