A Global and Local History of Drag Effects at IRIDIUM Mission Altitude

Empirical Validation of Design Principles for Survivable System Architecture

“…This research and related analyses [26] have concluded that the Iridium communications service is robust to node removal. For example, even with 36 of the 66 spacecraft removed, the system is still functional (i.e., packet delays do not exceed 178 milliseconds, well within an emergency value threshold of 400 ft) X sustains 9-g turns X X X two-tone grey camouflage (standard) X tail and wing proximity for enhanced maneuverability X X blended wing fuselage to reduce transonic drag X X X situational awareness data link X autonomous precision targeting (if necessary) X X X X bubble canopy for enhanced visibility X cockpit compatibility with night vision goggles X LANTIRN navigation pod for nighttime operations X modular avionics X X 30 degree seat back angle to increase g tolerance X ACES II ejection seat X buried fuel lines X X fuel inerting system X X X 29,000-pound engine thrust class X X thrust-to-weight ratio >1 X X fly-by-wire system for enhanced responsiveness X negative static stability for enhanced maneuverability X electronic-hydraulic stability augmentation system X fault tolerant control surfaces (aerodynamic redundancy) X X X X ground collision avoidance w/dissimilar-source validation X X X override feature of computer's alpha-limiter X redundant electrical generating and distribution equipment X four sealed-cell batteries for fly-by-wire system X two separate and independent hydraulic systems X X X M61 20-mm six-barrel rotary cannon X X X AIM-9 infrared, beyond-visual range a i r -t o -a i r m i s s i l e s X X X X rocket pods X X X anti-ship missiles X X X AGM-88 anti-radiation missiles X X X standoff precision strike weapo n s To test the baseline set of design principles, survivability features were gathered on the Iridium architecture from the literature [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37]. In tracing Iridium design features to the design principles, the unit of analysis is the overall communications network.…”

Simultaneous Orbit and Atmospheric Density Estimation for a Satellite Constellation

“…For many satellites in low earth orbit (LEO), the largest dynamic model uncertainty stems from atmospheric drag 1 . Acceleration due to atmospheric drag is related to atmospheric density by the equation (1) where is a drag coefficient, is the cross-sectional area of the satellite in the direction of travel, is the total spacecraft mass, is the velocity magnitude relative to the ambient atmosphere, and is a unit vector in the relative velocity direction. Uncertainty enters this equation in three ways.…”