# Aerospace
## 1 Introduction
Figure 3 shows a schematic of the drag-modulation aerocapture concept. In simple discrete event drag modulation, the ballistic coefficient is allowed to take two values, a low-value \(\beta_{1}\) with the drag skirt on and a high-value \(\beta_{2}\) after the drag skirt is jettisoned [13]. The only control variable is the time at which the drag skirt is jettisoned. Over the past several years, drag modulation has emerged as the preferred control technique over lift modulation for low-cost mission concepts due to its simplicity. Several recent studies have investigated the feasibility and guidance performance for drag-modulation aerocapture at Mars and Venus [14; 15; 16; 17; 18]. Several studies have proposed the use of small satellite constellations in low-circular orbits for future missions, but there are no studies investigating the use of aerocapture for planetary constellations. Some examples include: (1) a six-satellite constellation at Mars, which performs radio occultations using satellite cross-links to obtain hundreds of atmospheric profiles every day [19]; (2) a ten-satellite constellation at Mars to study the Martian climate system and volatile transport processes on a global scale [20]. The ability to establish constellations using small, low-cost satellites will enable a new paradigm in planetary exploration with global imaging and radar constellations that can image large portions of the planet in high cadence and detect surface changes, simultaneous multi-point observations of the magnetosphere, telecom relay networks, and satellite positioning systems [21]. The present study is the first to show how drag-modulation aerocapture when combined with very small B-plane targeting maneuvers allows the delivery of multiple  
Figure 3: Schematic showing the key events in drag-modulation aerocapture for small satellite orbit insertion. Distances are not to scale, and atmospheric extent is greatly exaggerated for clarity. small satellites to various inclination orbits from a single host spacecraft or a dedicated cruise stage and thus enable low-cost planetary constellations at Mars and Venus. The present work aims to provide the planetary science community with a detailed mission analysis of using a drag modulation system to insert multiple small satellites into low-circular orbits at Mars and Venus. A host spacecraft or dedicated cruise stage is assumed to carry the small satellite(s) and provide power and propulsion during the interplanetary cruise. A few days prior to reaching the planet, the carrier spacecraft releases the small satellite(s) for aerocapture and then performs a deflection maneuver to target its own approach trajectory to perform propulsive orbit insertion at periapsis. The small satellite deploys its drag skirt prior to entry and performs aero capture. A small propulsive Periapsis Raise Maneuver (PRM) at the first apoapsis is performed to raise the periapsis outside the atmosphere and complete its orbit insertion. The study is organized as follows. Detailed mission design and analysis are presented for a set of four small satellite concepts using aero capture for orbit insertion to low-circular orbits:  
1. A mission concept to deliver a single 25 kg small satellite to a 200 \(\times\) 2000 km near-equatorial Mars orbit as a secondary payload on a large orbiter mission. 2. A mission concept to deliver a single 25 kg small satellite to a 200 \(\times\) 2000 km polar Venus orbit as a secondary payload on a Venus orbiter mission. 3. A mission concept to deliver a constellation of five small satellites to various inclinations (equatorial to polar), 200 \(\times\) 2000 km Mars orbits as secondary payloads. 4. A mission concept to deliver a constellation of five small satellites, all to near-polar inclination, 200 \(\times\) 2000 km Venus orbits as secondary payloads on a Venus orbiter. Combining the \(\Delta V\) reduction from mission analysis and cost data published by [PERSON] et al.