Solar System Exploration

Scope on the Skies

Solar System Exploration

Science Scope—May/June 2022 (Volume 45, Issue 5)

By Bob Riddle

The year 2022 has been a banner year of sorts considering all the space missions launched so far and those scheduled later in the year. During the current fiscal year, which started October 2021, there will be more than one dozen missions related to science rather than flights to the International Space Station (ISS). NASA will be launching missions to study the Earth, our solar system, and beyond. For example, this past March, NASA launched the polar orbiting Joint Polar Satellite System-2 (JPSS-2) into a mission with instruments to measure and record ozone and ultraviolet levels in the atmosphere. Also included with the JPSS-2 was an interesting payload, the Low-Earth Orbit Flight Test of an Inflatable Decelerator (LOFTID). This is a test of a heat shield that could be used when landing heavy payloads on another world as opposed to using retrorockets or airbags. Another mission, the Parker Solar Probe, launched in 2018, is currently approaching its 12th orbital perihelion (closest to the Sun) during June. To reach solar orbit, the spacecraft followed a route that included six flybys of the planet Venus to slow the spacecraft down and adjust its solar orbital path. The mission has plans for a total of 24 perihelion and one more Venus encounter before the mission ends during June 2025. Coming as close as 4 million miles (2.4 million km) from the Sun, the Parker Solar Probe will provide data from its up-close observation of solar activity, leading us to a better understanding of space weather and how those events have an impact on the Earth (see Online Resources).

DART

Another mission, the Double Asteroid Redirection Test (DART) mission, launched last November, is enroute to Asteroid 65803 Didymos, an asteroid and its own moonlet traveling around the Sun together. The DART mission is the first test of a planetary defense mission where we will see if we can nudge an incoming asteroid away from impacting Earth. The DART spacecraft is nearly at its target, with arrival during this coming September when the DART spacecraft will impact the 500-foot (152 m) diameter moonlet at a speed of approximately 4 miles/sec. (2.4 km/sec.). Prior to impact, a CubeSat named LICIACube, built by the Italian Space Agency and equipped with cameras, will capture the impact. At the time of the impact, the asteroid will be approximately 6.8 million miles (11 million km) from the Earth and close enough for pictures to be taken by ground-based telescopes on Earth. As emphasized on the DART mission website, this asteroid and moonlet are not on a collision course for Earth impact (see Online Resources).

Psyche

The Psyche mission to Asteroid Psyche is scheduled for launch this summer and arrival at the asteroid during January 2026 (see Online Resources). Once settled into an orbit with the asteroid, the spacecraft will spend the following 21 months mapping and studying this asteroid. Why Asteroid Psyche? This asteroid is a metal-based asteroid rather than rock and ice and may represent what the core of the planetesimals are like, some of which have formed into the planets. Asteroid Psyche was discovered in 1852 by Annibale de Gasparis, an Italian astronomer. De Gasparis is credited for finding nine asteroids, of which Psyche—named after the goddess of the soul from Greek mythology—was his fifth (see Online Resources; see also Figure 1).

Lucy

Another asteroid-related mission, launched last October, is the Lucy mission to the Trojan Asteroids, a group of asteroids that travel with the planet Jupiter around the Sun. These asteroids are gathered into two groups at two of Jupiter’s Lagrange points, one group leading Jupiter and the other trailing Jupiter. Lagrange points are locations in space relative to a planet, where objects located at a Lagrange point essentially stay there as the objects are held in a balance between the planet and the Sun’s respective gravitational attraction. For example, the James Webb Space Telescope is located at one of the Earth’s Lagrange points. The Lucy spacecraft will follow a long 12-year journey that will take it to eight different asteroids including a main-belt asteroid as the spacecraft crosses the Main Asteroid Belt and seven of the Trojan asteroids (see Online Resources; see also Figure 1).

JUICE

Not to be outdone by NASA with clever acronyms for space missions, the European Space Agency (ESA) will be sending the JUICE (JUpiter ICy moons Explorer) spacecraft to the outer giant planet Jupiter. Instruments on board the spacecraft include several provided by NASA. Scheduled for launch this year and arrival at Jupiter by 2030, the JUICE spacecraft will orbit the Jovian system for at least three years observing Jupiter and three of its large moons, Ganymede, Calisto, and Europa. These moons are believed to have an internal ocean, which could also mean that conditions could be suitable for life. The JUICE mission will help us better understand planet formation and how that process may lead to the development of life (see Online Resources; see also Figure 1).

A few special days

During the coming two months there will be a few days on which we celebrate special events including the Earth, Space, and the Oceans. Some are serious and some are not so serious but still special; that being said, “May the 4th be with you!” And if you travel be sure to carry a towel, but most of all, “Don’t Panic!” (see Towel Day in Online Resources).

With a sort of space-related theme, these two months include National Astronaut Day (see Online Resources), celebrated on May 5 in an acknowledgment to the 1961 suborbital flight of Astronaut Alan Sheppard in Freedom 7. On that date, Alan Sheppard became the first person from our country in space when he was launched into a suborbital flight reaching an altitude of 116 miles and lasting about 15 minutes.

The first Friday in May is National Space Day (this year on May 6; see Online Resources). This is a day to acknowledge and celebrate our curiosity and exploration of the universe. National Space Day began in 1997 with a planned event sponsored by Lockheed Martin Corporation. A couple of years later, due to the influence of former Astronaut Senator John Glenn, National Space Day—originally called International Space Day—became an annual event.

Asteroid Day is celebrated annually on June 30. This is an international event sanctioned by the United Nations, and its mission is “to inspire, engage and educate the public about asteroids opportunities and risks” (see Online Resources).

World Oceans Day, another UN-sanctioned event, is celebrated on June 8. World Oceans Day is significant as it “provides an opportunity to celebrate the importance of the ocean and to better understand how to interact with oceans in a sustainable manner” (see Online Resources).

“Got a second?”

Although perhaps not an official “day,” June 30 is the 50th anniversary of the introduction of the Leap Second into our vocabulary and our lives. Started in 1972 by the International Earth Rotation and Reference Systems Service (IERS), the leap second is used to correct the difference between UTC (Coordinated Universal Time) and UTI (Astronomical Time). UTC is atomic clock–based and is used, among other purposes, to calibrate UTI. UTC is also used for determining when to insert a Leap Second. UTI, or Astronomical Time, may be familiar to some as what was once called Greenwich Mean Time. This is where time is based on the rotation of the Earth and the 0° longitude of Greenwich England as the reference for time zones around the Earth (see Online Resources).

Total lunar eclipse

What celestial event happens when the Moon, at or near full phase, finds itself at a node crossing? The subheading should be a giveaway; however, not all lunar eclipses are total. This eclipse will be visible for much of the Americas, North and South, and unlike the partial lunar eclipse of last November, which occurred after midnight, this one is a total lunar eclipse and occurs, for the most part, before midnight as the full Moon rises in the east (see eclipse timetable in Figure 2). For a lunar eclipse to happen, either as a partial or total, the Moon must be at or close to the time of its full phase. The Moon also must be at the point in its orbit where the Moon’s orbital path intersects the Earth’s orbital path—the ecliptic. The intersection of the two orbital paths is a result of the Moon’s orbital path inclined from the ecliptic by about 6°. There are two of these intersections, and they are called nodes—an ascending node and a descending node. During this eclipse the Moon will be at its descending node (see Figure 3).