Priority targets
The 30 most concerning derelict objects
In 2021, eleven international teams independently ranked the dead objects in low Earth orbit most likely to start a cascade, weighing mass, encounter rate, orbital lifetime and proximity to working satellites. The composite list is dominated by nine-tonne Zenit upper stages parked at 830–850 km. Why this list matters.
| # | NORAD | Object | Mass kg | Perigee × apogee km | Incl ° | Owner | Launched |
|---|---|---|---|---|---|---|---|
| 1 | 22566 | SL-16 R/B | 9,000 | 837 × 848 | 71 | CIS | 1993-03-26 |
| 2 | 22220 | SL-16 R/B | 9,000 | 827 × 848 | 71 | CIS | 1992-11-17 |
| 3 | 31793 | SL-16 R/B | 9,000 | 843 × 846 | 71 | CIS | 2007-06-29 |
| 4 | 26070 | SL-16 R/B | 9,000 | 827 × 854 | 71 | CIS | 2000-03-02 |
| 5 | 16182 | SL-16 R/B | 9,000 | 833 × 844 | 71 | CIS | 1985-10-22 |
| 6 | 20625 | SL-16 R/B | 9,000 | 834 × 853 | 71 | CIS | 1990-05-22 |
| 7 | 27006 | SL-16 R/B | 9,000 | 986 × 1,006 | 99.5 | CIS | 2001-10-12 |
| 8 | 23705 | SL-16 R/B | 9,000 | 831 × 852 | 71 | CIS | 1995-10-31 |
| 9 | 25407 | SL-16 R/B | 9,000 | 835 × 844 | 71 | CIS | 1998-07-28 |
| 10 | 23405 | SL-16 R/B | 9,000 | 838 × 845 | 71 | CIS | 1994-11-24 |
| 11 | 17974 | SL-16 R/B | 9,000 | 823 × 846 | 71 | CIS | 1987-05-13 |
| 12 | 23088 | SL-16 R/B | 9,000 | 841 × 845 | 71 | CIS | 1994-04-23 |
| 13 | 22285 | SL-16 R/B | 9,000 | 840 × 844 | 71 | CIS | 1992-12-25 |
| 14 | 22803 | SL-16 R/B | 9,000 | 823 × 850 | 71 | CIS | 1993-09-16 |
| 15 | 19650 | SL-16 R/B | 9,000 | 831 × 848 | 71 | CIS | 1988-11-23 |
| 16 | 24298 | SL-16 R/B | 9,000 | 839 × 863 | 70.8 | CIS | 1996-04-09 |
| 17 | 28353 | SL-16 R/B | 9,000 | 842 × 848 | 71 | CIS | 2004-10-06 |
| 18 | 17590 | SL-16 R/B | 9,000 | 831 × 841 | 71 | CIS | 1987-03-18 |
| 19 | 19120 | SL-16 R/B | 9,000 | 814 × 842 | 71 | CIS | 1988-05-15 |
| 20 | 25400 | SL-16 R/B | 9,000 | 801 × 813 | 98.6 | CIS | 1998-10-07 |
| 21 | 27386 | ENVISAT | 7,800 | 764 × 766 | 98.1 | ESA | 2002 |
| 22 | 27001 | METEOR 3M | 2,500 | 994 × 1,013 | 99.6 | CIS | 2001-10-12 |
| 23 | 24277 | ADEOS | 3,560 | 793 × 794 | 98.9 | Japan | 1996-08-17 |
| 24 | 27601 | H-2A R/B | 3,000 | 734 × 836 | 98.2 | Japan | 2002-12-14 |
| 25 | 15334 | SL-12 R/B(2) | 2,440 | 838 × 847 | 71 | CIS | 1984-09-28 |
| 26 | 37932 | CZ-2D R/B | 4,000 | 791 × 846 | 98.7 | China | 2011-11-20 |
| 27 | 10732 | SL-8 R/B (Kosmos-3M stage) | 1,435 | 966 × 995 | 82.9 | CIS | 1978-03-15 |
| 28 | 24279 | H-2 R/B | 2,700 | 860 × 1,306 | 98.7 | Japan | 1996-08-17 |
| 29 | 23704 | COSMOS 2322 | 3,250 | 842 × 854 | 71 | CIS | 1995-10-31 |
| 30 | 21090 | SL-8 R/B | 1,435 | 961 × 992 | 82.9 | CIS | 1991-05-02 |
Source: McKnight et al., "Identifying the 50 statistically-most-concerning derelict objects in LEO", Acta Astronautica 181 (2021), open PDF. Orbits as of 2020.