It is well known that the asteroid (99942) Apophis will have a very close approach with the Earth on 13 April 2029. The object will pass at a distance less than that at which the geostationary satellites orbit the Earth and will be visible to the naked eye from some parts of the world. Such a close approach by an object the size of Apophis typically occurs only once every 10 000 years.

To take advantage of this opportunity, ESA, NASA and other space agencies are planning dedicated space missions, or have extended other missions (as in the case of OSIRIS-REx, which is now called OSIRIS-APEX), to reach Apophis around this epoch.

While the case of Apophis in 2029 is certainly very noteworthy, it is also interesting to realise that in the period between mid of 2027 and the end of 2029 there will be several large NEAs that will have close approaches with the Earth (see figure below). In fact, during this 2-year period, the following five large known NEAs (in addition to Apophis) will pass within four lunar distances (LD) of Earth:

• (153814) 2001 WN5, with a diameter of 930 m and passing at 0.65 LD on 26 June 2028,
• (137108) 1999 AN10, with an estimated diameter of 800 m and passing at 1.01 LD on 7 August 2027,
• (35396) 1997 XF11, with a diameter of 700 m and passing at 2.42 LD on 26 October 2028,
• (292220) 2006 SU49, with an estimated diameter of 400 m and passing at 3.19 LD on 28 January 2029, and
• 2023 GQ2, with an estimated diameter of 400 m and passing at 3.95 LD on 16 November 2028.

If a rendezvous mission to one of these bodies were planned, the delta-V requirements for such a mission would be between 5 km/s and 15 km/s. For asteroid missions after Apophis, the situation is not exactly the same as in the 2-year interval mentioned, but there are still feasible candidates. These can be seen in the figure below, where the following medium to large objects will have approaches to Earth of less than 5 LD by 2040:

• 2002 NY40, with a diameter of 280 m and passing at 2.8 LD on 11 February 2038,
• 2021 TG4, with an estimated diameter of 400 m and passing at 2.9 LD on 4 May 2034,
• (536531) 2015 DV215, with an estimated diameter of 290 m and passing at 2.9 LD on 6 October 2035,
• (613403) 2006 GB, with an estimated diameter of 300 m and passing at 4.1 LD on 22 March 2037,
• 2021 PC7, with an estimated diameter of 500 m and passing at 4.2 LD on 16 September 2033,
• (216985) 2000 QK130, with an estimated diameter of 200 m and passing at 4.4 LD on 15 March 2036,
• (369057) 2008 DK5, with an estimated diameter of 200 m and passing at 4.5 LD on 28 February 2039,
• (549948) 2011 WL2, with an estimated diameter of 250 m and passing at 4.7 LD on 21 April 2038,
• 2019 OQ2, with an estimated diameter of 300 m and passing at 4.8 LD on 04 April 2039.

Therefore, alternative mission options could be flown to the above objects, which could also be filtered in terms of the delta-V required to reach them, and also in terms of their taxonomy and other properties.

Caption: Close approaches of known large NEAs by 2040 and the approximate delta-V required for a rendezvous mission. Plot based on an idea by Dotson et al. 2022. Credits: ESA / PDO