Development of a Sun Synchronous. Conjunctions

Transcription

1 Development of a Sun Synchronous Zoning Architecture to Minimize Conjunctions Kevin Shortt Brian Weeden Secure World Foundation

2 Overview Current Situation in Sun synchronous Orbit Orbital Mechanics that drive SSO Mission Design Proposed Slot Architecture Methodology Way Ahead 2

3 CURRENT SITUATION What is the problem we are trying to solve? 3

4 Overall Orbital Debris Situation 4

5 km objects All Objects in Near Polar LEO By Apogee 4,92 total objects Catalog data accurate Aug 2007 Near-Polar LEO defined as inclinations between 96.5 and 02.5 and apogees less than 2,000 km cts 00 Number of Obje Apogee (kilometers) 5

6 All Objects in Near Polar LEO By Inclination 400 cts Number of Obje objects objects objects 4,92 total objects Catalog data accurate Aug 2007 Near-Polar LEO defined as inclinations between 96.5 and 02.5 and apogees less than 2,000 km Inclination (degrees) 6

7 All Active Spacecraft in Near Polar LEO by Apogee km 5 sats 38 total objects ites umber of Satell N Catalog data accurate Aug 2007 Near-Polar LEO defined as inclinations between 96.5 and 02.5 and apogees less than 2,000 km Apogee (kilometers) 7

8 All Active Spacecraft in Near Polar LEO by Inclination 40 ites Number of Satell sats 38 total objects Catalog data accurate Aug 2007 Near-Polar LEO defined as inclinations between 96.5 and 02.5 and apogees less than 2,000 km Inclination (degrees) 8

9 All Active SSO Spacecraft Promoting Cooperative Solutions for Space Security Canadian Space Society 9

10 Cloudsat vs Sinah NASA Cloudsat and Iranian Sinah 6 July 2007, Close approach of 00 meters 4 July Cloudsat maneuver increased miss distance to 4 km Maneuvered again on 7 July to return to formation (part of A Train) 0

11 ORBITAL MECHANICS OF SSO MISSION DESIGN What are the orbital mechanics behind this distribution pattern?

12 Precession Rate Sun synchronous means the satellite crosses the Equator at the same local Solar time each day Achieved by precessing the satellite orbit Westward around the Equator at deg/day Fixes Inclination and Altitude Boain 2004 pg 4 2

13 Repeating Ground Track Integer number of Equator crossing before the satellite starts to repeat its ground track Hl Helps dfi define the temporal resolution of the satellite Fixes Inclination and Altitude 3

14 Mean Local Time MLT is the mean local solar time when the satellite will cross a given point on the Equator Set by the right ascension of the ascending node, usually at launch Vallado 2007 pg 853 Fixes RAAN 4

15 Frozen Orbit e = 0.00 ω = 90 Vallado (2007) pg 876 Perturbations can effect the various orbital parameters over time Primary concern for most SSO applications are variations in altitude over target and apsidal line rotation Orbits can be designed such that perturbations act to cancel out global variations and in effect freeze the desired parameters Fixes Eccentricity and Argument of Perigee 5

16 PROPOSED SLOT ARCHITECTURE METHODOLOGY 6

17 Three Pronged Solution Minimizes creation of future debris IADC success World-wide Implementation starting Near-Term Removes existing debris from orbit IAA study ongoing, results due mid 2009 Long-Term Development of a Sun-synchronous zoning architecture is proposed as one part of a Space Traffic Management System Debris Removal Debris Mitigation Space Traffic Management Minimizes effects of debris on spacecraft Mid-Term Minimizes the chances of collisions between spacecraft Allows O/O to plan avoidance and station-keeping maneuvers with better accuracy 7

18 Methodology Narrow the set of all possible Sun synchronous orbits into a workable set that can be crystallized into a slot architecture. Start with SSO continuum 2. Find all integer RGTs between x and y number of days and within min/max altitudes (-20 days and 400-,400 km = 370 unique RGTs) 3. Filter for a certain spacing in altitude (based on positional accuracy + safety margin) 4. Space satellites within each orbital plane in anomaly (60?)

19 Naming Convention Slots could be named using their RGT, right ascension (referenced to noon), and anomaly 2D = 2 Day 25 rev repeat, 0900 local Equator crossing time, satellite located 60 degrees from perigee 9

20 NEXT STEPS 20

21 Future Questions to Answer Can we quantify the actual benefit? How much inflexibility can mission designers tolerate? What are the effects of station keeping maneuvers on the slot architecture? Phasing of slots at the poles 2

22 References Boain, Ronald, A B Cs of Sun Synchronous Orbit Mission Design, 4 th AIS/AIAA Space Flight Mechanics Conference (2004) Vallado, David, Fundamentals of Astrodynamics and Applications, 3 rd Ed. (2007) Wertz, James and Larson, Wiley, Space Mission Analysis and Design, 3 rd Ed. (999) Special thanks to AGI for use of their Satellite Tool Kit software. 22

23 Questions? Thank you for our time and we encourage feedback and comments 23