Question E2A01:
What is the direction of an ascending pass for an amateur satellite?  

Choices:  
A: From west to east  
B: From east to west  
C: From south to north  
D: From north to south    

Correct Answer is  C: From south to north  

To understand “ascending pass,” remember the definition of the ascending node: the point where a satellite crosses Earth’s equator going from the Southern Hemisphere to the Northern Hemisphere. During an ascending pass, the satellite’s latitude is increasing.

Why the correct answer is correct:
- From south to north is the definition of an ascending pass. The satellite crosses the equator northbound, so its latitude increases:  
  $$\text{Ascending if } \frac{d(\text{latitude})}{dt} > 0$$

Why the other choices are incorrect:
- From west to east (A): This describes a prograde (eastward) ground-track component, not whether the pass is ascending or descending. A pass can be ascending or descending regardless of east/west motion.
- From east to west (B): This describes a retrograde (westward) ground-track component, not ascending/descending. Again, independent of north/south direction.
- From north to south (D): That’s a descending pass (latitude decreasing), the opposite of ascending.

Useful rules of thumb:
- Ascending = south → north; descending = north → south.
- East/west describes orbital direction relative to Earth’s rotation, not ascending/descending:
  - Prograde + ascending often looks SW → NE to an observer.
  - Retrograde + ascending often looks SE → NW.
- The ascending node is where the orbital plane crosses the equator northbound; its angle is the RAAN (Right Ascension of the Ascending Node), often denoted $\Omega$.