EscaPADE (Escape and Plasma Acceleration and Dynamics Explorers)

Quick facts

Overview

Summary

Mission Capabilities

Each EscaPADE spacecraft houses three science instruments: EMAG (Escapade MAGnetometer), which aims to quantify Mars’ magnetic field; EESA (Escapade ElectroStatic Analyzers), a set of two electrostatic analysers that will observe suprathermal ions and electrons; and ELP (Escapade Langmuir Probe) Suite, which will measure solar wind and the plasma environment.
EscaPADE will primarily measure ion escape and sputtering, which are driven by interactions of the Martian atmosphere with solar wind and the interplanetary magnetic field (IMF). The mission provides continuity to NASA’s MAVEN mission, which aims to investigate the loss of atmospheric gas to space and how it affected the Martian climate.

Mission Overview

EscaPADE’s mission will be divided into seven phases over about 2.5 years: launch and orbit raise, interplanetary cruise, Mars orbit insertion (MOI), orbit reduction, transition to science formation (TSF), primary science, and decommissioning.  

The EscaPADE 11-month primary science phase will consist of two science campaigns. Science Campaign A will make observations of dynamic ionospheric properties of Mars for six months, which will be facilitated by a leader-follower spacecraft flying configuration. Blue will lead Gold from the same orbit with a periapsis of 160 km and an apoapsis of 8400 km, with a temporal separation that oscillates between zero and 30 minutes. 

Science Campaign B will see the spacecraft operate from different orbits over a five month period, in order to measure spatially varying properties of Mars’ near-space environment. The transition to Science Campaign B will involve Gold lowering its apoapsis to 7000 km, while Blue raises its apoapsis to 10,000 km. Both spacecraft will maintain a periapsis of 160 km and each will become managed independently.

Space and Hardware Components

The EscaPADE spacecraft are based on a sub-90 kg Rocket Lab Photon bus. Fixed solar arrays will provide 260 W of power, and Rocket Lab bi-propellant HyperCurie engines will propel the spacecraft. 
 

Overview

Escape, Plasma, and Acceleration Dynamics Explorers (EscaPADE) is a dual-spacecraft mission of NASA under the Small Innovative Missions for Planetary Exploration (SIMPLEx) programme. EscaPADE will build an understanding of the structure, composition, and dynamics of Mars’ hybrid magnetosphere, alongside investigating the flow of solar wind through it and how it drives the loss of the planet’s atmosphere. The mission is led by the University of California (UC) Berkeley, and its design by the commercial company Advanced Space, with spacecraft navigation provided by both organisations. Rocket Lab provides the mission’s spacecraft buses, which are based on their Photon platform with Martian modifications. Communications are facilitated by NASA’s Deep Space Network (DSN). 1) 2) 3) 4) 5) 6)

The mission intends to augment observations made by NASA’s Mars Atmosphere Volatile and EvolutioN (MAVEN) mission, at a fraction of the cost. MAVEN has the objective to investigate the loss of the Martian atmosphere, through four main processes. Two of which are photochemical escape of Oxygen, Carbon and Nitrogen, and Jeans escape; these are driven mostly by radiation from the sun in the form of extreme ultraviolet (EUV), and the Martian seasons. 5)

EscaPADE will investigate the other two processes affecting the loss of the Martian atmosphere, ion escape and sputtering. These are primarily driven by the motion of ions in the upper Martian atmosphere and the result of interactions between this region and the Martian ionosphere with the solar wind and interplanetary magnetic field (IMF). The resultant electric and magnetic fields drive ion escape, whereby natural atoms from the thermosphere are ionised, imparting them with sufficient energy to escape Mars’ gravitational influence. The fields also drive sputtering, where neutral atoms are ionised except this time they accelerate back toward the atmosphere where they collide with thermospheric neutral atoms, giving them energy to escape. Sputtering cannot yet be directly observed, so escape rates are derived from precipitating ion spectra. Observation of these variables will help build a picture of the Martian climate’s evolution over the planet’s history. 5) 7)

EscaPADE will further build upon knowledge obtained through other space environment missions, such as Cluster, THEMIS, Van Allen Probes, and the Magnetospheric MultiScale (MMS) Constellation, which investigated a variety of plasma phenomena in the terrestrial magnetospheric environment. EscaPADE will measure magnetic field strength and topology, ion plasma distributions, suprathermal electron flows, and thermal electron and ion densities.

Spacecraft

UC Berkeley were awarded the contract to design two Photon spacecraft for a Martian mission in 2021, which could leverage a unique dual viewpoint on the Martian environment to probe magnetospheric phenomena. The mission will consist of two identical spacecraft, dubbed ‘Blue’ and ‘Gold’ named after the UC Berkeley colours, with platform masses under 90 kg each. EscaPADE is a Class D mission of NASA (high risk tolerance mission). 3) 8) 9)

The EscaPADE spacecrafts feature fixed solar arrays delivering 260 W of solar power, tilted to a fixed angle such to maximise solar illumination while minimising charging and noise, a 50 cm fixed antenna, and continuous in-situ data collection. Propulsion is provided by bi-propellant Rocket Lab HyperCurie engines capable of achieving greater than 2500 m/s ΔV, as well as a cold nitrogen gas reaction control system (RCS) for small manoeuvres and an alternative to the reaction wheels. 8) 10)

There are three science instruments onboard the spacecraft, two of which are mounted on a 2 m boom: EMAG (Escapade MAGnetometer) and multi-needle Langmuir Probe (mNLP) of the ELP (Escapade Langmuir Probe) Suite. The third, EESA (Escapade ElectroStatic Analyzers) is mounted on the upper deck of the spacecraft platform. 2) 4)

Communications are facilitated by an X-band system alongside two ranging transceivers for deep space navigation. A high-gain array antenna is used to communicate science data to the DSN on Earth and another four low-gain and two medium-gain antennas to maintain communication when the spacecraft is not pointing at Earth. 10)

Launch

The EscaPADE spacecraft are designed to be launched in a rideshare configuration, from a number of possible configurations, including: 5)

• Direct-to-Mars rideshare
• Earth Orbit rideshare with an additional boost
• Other rideshare opportunities (i.e. lunar flyby)

Orbit

The spacecraft are intended to gather Martian atmospheric data from the same elliptical orbit over the course of six months. The two will then move to different science orbits to make simultaneous observations of the atmosphere over the next five months, with the possibility for a mission extension. 5)

Mission Phases

The EscaPADE mission is split up into seven phases, starting with its launch from Earth and finishing with decommissioning after the primary science is complete.

Launch and Orbit Raise

The first phase of EscaPADE’s mission involves the launch of both the Blue and Gold spacecraft from Earth, their commissioning phases, and the manoeuvres required to initiate their interplanetary cruise. The spacecraft will be launched into an initial Sun-synchronous orbit as secondary payloads on a rideshare mission. The orbits of each spacecraft will then be systematically raised prior to trans-Mars injection (TMI), of which Blue will enter 48 hours prior to Gold. 5)

The design of EscaPADE permits TMI starting from various potential Earth orbits thanks to a general-purpose orbit raise and plane change approach.

Interplanetary Cruise

The two spacecraft will travel to Mars in a Type II transfer, which has a longer duration than Type I transfers, but delivers spacecraft with a lower arrival velocity, which better suits orbital missions. NASA’s Deep Space Network (DSN) will communicate with both spacecraft simultaneously, termed multiple spacecraft per aperture (MSPA), once they are one third of the way to Mars, and a sufficiently small angular size in the sky.  5) 11)

Blue will perform its TMI first (TMI-B), but will arrive after Gold in order to satisfy the trajectory correction manoeuvre (TCM) budget.

Mars Orbit Insertion

The Mars Orbit Insertion (MOI) for the two EscaPADE spacecraft will be separated by 48 hours as done with TMI, which reduces the cost needed during the mission’s interplanetary cruise to establish MSPA. The MOI consists of inertially fixed manoeuvres designed to inject the spacecraft into Mars capture orbits with 60 hour periods, and is planned to commence approximately one month prior to the mission’s arrival. Both spacecraft will target an altitude of 450 km above the Martian surface, and will be performed by an inertially-pointed chemical propulsion burn. As the spacecraft enter the Mars capture orbit, instruments can be tested and calibrated as they pass through unimpeded solar wind at Mars apoapsis (known as apoareion) and the Martian magnetosphere at Mars periapsis (periareion). Phase three is completed when the spacecraft have entered safe and stable orbits around Mars. 5)

Orbit Reduction

Upon the completion of MOI, the EscaPADE spacecraft will reduce the size of their orbits through a series of burns, placing them in safer orbits and correcting any insertion errors. Each spacecraft will perform an apoapse reduction manoeuvre (ARM), coast for two weeks, then perform a periapse reduction manoeuvre (PRM). The ARMs target a desired orbital period while the PRMs target a periapse altitude. These manoeuvres are designed such that the orbits do not intersect and the spacecraft have no chance of collision. 5)

During Phase Four, the mission will experience a solar conjunction, which occurs when the spacecraft are positioned on the opposite side of the Sun from Earth, thereby limiting communication capabilities. Throughout this period, both the Blue and Gold spacecraft will maintain safe and stable orbits.

Transition to Science Formation

At the end of the solar conjunction, Blue and Gold will begin their transition to science formation (TSF) phase, through the lowering of their altitude to an orbit of 8,400 km x 160 km. Both spacecraft will be inserted into this orbit as they target a leader-follower flying formation with a 0 - 30 minute separation, with Blue leading. This is achieved by matching orbital periods, planes (within one degree), and apoapsis altitudes (within 10 km). The TSF phase is expected to consist of eight or nine burns.

Primary Science

EscaPADE’s primary science phase has an 11-month duration split into two science campaigns; six months in Campaign A and five in Campaign B. The phase commences once the spacecraft have established their leader-follower flying formation. Science Campaign B requires the satellites having different apoapse altitudes, in which Blue raises its apoapse to 10,000 km and Gold reduces to 7,000 km.

Science Campaign A involves the measurement of dynamic properties of the Martian environment through observations of the same region with a temporal separation. The leader-follower or ‘string-of-pearls’ flying formation with a variable separation will allow for time-varying processes to be investigated. The orbit selected for Science Campaign A is such that the spacecraft traverse through the maximum ion density. With the spacecraft operating independently from different orbits in Science Campaign B, the mission will investigate spatially varying properties of Mars’ near-space environment.  5)

Decommissioning

The EscaPADE spacecraft will be retired at the end of the mission according to NASA policy, degrading their orbits passively and eventually burning up upon entering the Martian atmosphere. 5)

Sensor Complement (EMAG, EESA, ELP)

EMAG (Escapade MAGnetometer)

EMAG will be mounted on the two metre boom arm that extends from the bodies of the EscaPADE spacecraft. The instrument will make measurements of Mars’ magnetic field from 0 - 2 μT, with an accuracy of 0.5 nT and angular resolution of 20° for field strengths above 1 nT. EMAG was developed by NASA GSFC. 2) 12)

EESA (Escapade ElectroStatic Analyzers)

EESA consists of two electrostatic analysers to detect suprathermal ions (EESA-i) and electrons (EESA-e). EESA-i will measure ion energetics between 0.5 eV - 30 keV and EESA-e will measure electron energetics between 10 eV and 10 keV. Both instruments have an energy resolution (ΔE/E) of 17% and angular resolution of 23°x 23°. EESA-e has a pitch-angle distribution (PAD) ranging from 20 - 160°. EESA was developed by UCB SSL. 12)

ELP (Escapade Langmuir Probe) Suite

Langmuir probes are devices designed to measure properties of electrons and ions, including their temperature and density through measurements of current and voltage. Their I-V characteristic will depend on these plasma parameters which is how they are deduced. 13)

EscaPADE’s LP will measure thermal plasma in Mars’ space environment, at particle densities ranging from 50 - 200,000 particles per cm3. The instrument suite includes a set of Planar Ion Probes (PIPs) to measure Solar Extreme Ultraviolet (EUV) flux, a Floating Potential Probe (FPP) to measure the potential of the spacecraft relative to the surrounding plasma, and a multi-needle Langmuir Probe (mNLP) to measure thermal plasma density. The ELP suite was developed by the Embry-Riddle Aeronautical University (ERAU), Florida. 12)

Ground Segment

Communications and ground tracking network operations are facilitated by NASA’s Deep Space Network (DSN), which will send and receive TT&C (Telemetry, Tracking and Command) data from the EscaPADE spacecraft throughout the mission lifetime.

References

1) “EscaPADE,” NASA Science, URL: https://science.nasa.gov/mission/escapade/

2) “ESCAPADE Spacecraft,” NASA Space Science Data Coordinated Archive, October 28, 2022, URL: https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=ESCAPADE

3) “Mission to Mars - EscaPADE,” Rocket Lab, URL: https://www.rocketlabusa.com/missions/upcoming-missions/misson-to-mars-escapade/

4) Lillis RJ, Curry SM, Ma YJ, Curtis DW, Taylor ER, Parker JS, Hara T, Luhmann JG, Barjatya A, Larson DE, Livi R. “ESCAPADE: A Twin-Spacecraft Simplex Mission to Unveil Mars' Unique Hybrid Magnetosphere,” Low-Cost Science Mission Concepts for Mars Exploration. 2022 Mar;2655:5012, URL: https://www.hou.usra.edu/meetings/lpsc2022/pdf/1135.pdf

5) Parker JS, Lillis R, Curry S, Ott C, Kohler A, Rosen M. “ESCAPADE: A Low-Cost Formation at Mars,” Proceedings of the 73rd International Astronautical Congress (IAC); September 2022

6) Richard French, Ehson Mosleh, Christophe Mandy, Richard Hunter, Jonathan Currie, Doug Sinclair, Peter Beck, “Bringing Deep Space Missions within Reach for Small Spacecraft,” Rocket Lab, URL: https://digitalcommons.usu.edu/smallsat/2021/all2021/158/

7) Lillis, R., Curry, S., Luhmann, J., Ma, Y., Barjatya, A., Whittlesey, P., Livi, R., Larson, D., Xu, S., Russell, C., Fowler, C., Brain, D., Thiemann, E., Withers, P., Modolo, R., Harada, Y., and Berthomier, M.: ESCAPADE: Coordinated multipoint measurements of Mars' unique hybrid magnetosphere, Europlanet Science Congress 2020, online, 21 Sep–9 Oct 2020, EPSC2020-511, https://doi.org/10.5194/epsc2020-511, 2020

8) “ESCAPADE,” University of California Berkeley Space Sciences Laboratory, URL: https://escapade.ssl.berkeley.edu/

9) “NASA Launch Services Risk Classification Fact Sheet,” URL: https://www.nasa.gov/wp-content/uploads/2023/12/risk-classification-fact-sheet.pdf

10) Richard French, Ehson Mosleh, Christophe Mandy, Richard Hunter, Jonathan Currie, Doug Sinclair, Peter Beck, “Bringing Deep Space Missions Within Reach for Small Spacecraft,” Rocket Lab, 35th Annual Small Satellite Conference, URL: https://digitalcommons.usu.edu/smallsat/2021/all2021/158/

11) “‘Porkchop’ is the First Menu Item on a Trip to Mars,” NASA’s Mars Exploration Program, URL: https://mars.nasa.gov/spotlight/porkchopAll.html

12) “ESCAPADE Instruments,” University of California Berkeley Space Sciences Lab, URL: https://escapade.ssl.berkeley.edu/instruments/

13) Zsolt Váradi, “Langmuir Probe,” ESA, URL: https://www.esa.int/Education/ESEO/Langmuir_Probe