AERO2705 – week 3.

Locations in orbit relative to earth.

Where is ISS orbit?

What are the properties of the orbit?

Where is ISS in this orbit?

How does this synchronise with Locations on earth?

Use TLE predictors.

http://www.satflare.com/track.asp ISS (ZARYA) 1 25544U 98067A 14230.18630382 .00006387 00000-0 11950-3 0 9152 2 25544 51.6464 152.2622 0004410 35.3455 111.7757 15.50072726900948 Orbit prediction systems.

• NASA Jtrack-3D

• Orbitron Two Line Element Coding of Satellite Ephemeris Data

Line 1 Column 1 Line Number Column 3-->7 Satellite Number Column 8 Classification Column 10-->11 Launch Year Column 12-->14 Launch Number Column 15-->17 Launch Component Column 19-->20 Epoch Year Column 21-->32 Epoch Day Column 34-->43 Decay Rate Column 45-->52 Rate of Decay Rate Column 54-->61 BSTAR drag Column 63 Ephemeris type Column 65-->68 TLE set number Column 69 Checksum Line 2 Column 1 Line Number Column 3-->7 Satellite Number Column 9-->16 Orbit Inclination Column 18-->25 Location of the Ascending Node (degrees) relative to V.E. Column 27-->33 Eccentricity Column 35-->42 Argument of Perigee (degrees) Relative to V.E. Column 44-->51 Mean Anomaly (degrees) Column 53-->63 Mean Motion (revs per day) Column 64-->68 Rev number at Epoch Column 69 Checksum

Simulation software can TLE info to predict orbits into the future. Eg orbitron.exe.

30 days between TLE updates. Orbital Perturbations.

Small purturbations due to Sun and Moon cause the orbital plane to rotate. → changes ascending node and location of perigee.

Irregularity in earth's shape has a significant influence → changes ascending node and location of perigee. → dominant influence for MEO, LEO orbits.

Atmospheric Drag → causes LEO orbits to decay significantly.

Human or planned intervention. → Orbital Boosts, changes in inclination, changes in perigee of orbital plane. → impact with space debris.