Orbiting satellite ke liye centripetal force kaun si force provide karti hai?
Gravity: GMm/r2=mv2/r.
Circular orbital speed ka formula?
v=μ/r (altitude ke saath decrease karta hai).
Orbital period ka formula (circular)?
T=2πr3/μ (Kepler's 3rd law).
GEO altitude aur kyun?
~35 786 km, kyunki period ek sidereal day (86 164 s) ke barabar hona chahiye.
GEO ke liye sidereal vs solar day?
Sidereal use karo (86 164 s); Earth Sun ke around bhi orbit karta hai isliye solar day zyada lamba hota hai.
Geostationary vs geosynchronous mein kya fark hai?
Dono ka period = sidereal day; geostationary mein additionally e=0,i=0 hota hai isliye ye ek equatorial point ke upar fixed rehta hai.
Koi orbit Sun-synchronous kya banata hai?
Uski J2 nodal precession Earth ke ~0.9856°/day Sun ke around motion ke barabar hoti hai, local Sun time constant rakhti hai.
SSO retrograde (~98°) kyun hona chahiye?
cosi negative hona chahiye taaki Sun se match karti eastward precession mile.
Molniya inclination aur kyun?
63.4°, critical inclination jahan 5cos2i−1=0 toh perigee drift nahi karta.
Molniya period?
Half a sidereal day (~12 h) high northern apogee ke saath long loiter ke liye.
GPS kaunsi orbit mein hai aur kitni altitude par?
MEO, ~20 200 km, ~12-h period.
Semi-major axis apogee & perigee radii ke terms mein?
a=(ra+rp)/2.
Satellite apogee par sabse slow kyun chalti hai?
Kepler's 2nd law: equal areas in equal times → slow jab door ho.
Recall Feynman: 12-saal ke bachche ko samjhao
Socho tum ek ball ko string par ghuma rahe ho circle mein. Gravity string hai. Agar Earth ke paas ho, gravity zyada kheenchti hai, isliye bahut tezi se ghoomna padta hai — ye low satellite hai jo 90 minute mein ek chakkar lagata hai. Bahut upar gravity ek kamzor string hai, isliye ball dheere drift karta hai — GEO ek pura din leta hai, isliye ek TV dish ek jagah point kar sakta hai hamesha ke liye aur hilata nahi. Kuch satellites ek squished loop ke ek taraf pe aaram se chalti hain: neeche se tezi se guzarti hain aur phir upar bahut door pe ghanton tak aaram karti hain, taaki woh thande northern countries ko dekh sakein — ye Molniya hai. Aur Earth ka thoda-mota middle ek gentle push deta hai jise hum cleverly use karte hain taaki ek tarah ka satellite hamesha din ke same waqt zameen dekhta rahe, photo compare karne ke liye perfect.
