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:
“Science is a dynamic undertaking directed to lowering the degree of the empiricism involved in solving problems; or, if you prefer, science is a process of fabricating a web of interconnected concepts and conceptual schemes arising from experiments and observations and fruitful of further experiments and observations.”
—James Conant (1893–1978)
“I’ve been asked to give some words of advice for young women entering library/information science education. Does anyone ever take advice? The advice we give is usually what we would do or would have done if we had the chance, and the advice that’s taken, if ever, is often what we wanted to hear in the first place.”
—Phyllis Dain (b. 1930)
“It is not too much to say that next after the passion to learn there is no quality so indispensable to the successful prosecution of science as imagination. Find me a people whose early medicine is not mixed up with magic and incantations, and I will find you a people devoid of all scientific ability.”
—Charles Sanders Peirce (1839–1914)