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Legend - object IDs

Data compiled at 2046 UTC on 6 Aug. 2020 for 28 known objects during a period of seven days from 3 to 9 Aug. 2020. Orange is for objects with a new JPL orbit solution (usually from new observation).

Chart
ID

Full ID
Period
Closest
Passage
Uncertainty

Status
MX32020 MX312.47 LD  departed
NZ2020 NZ13.28 LD  departed
OA62020 OA66.35 LDoutbound
OB52020 OB534.1 LD+/- 1.0167 hours  departed
OC2020 OC23.92 LD  departed
OC12020 OC19.81 LD  departed
OD2020 OD21.73 LD  departed
OE22020 OE25.84 LDoutbound
OG32020 OG37.09 LDoutbound
OH22020 OH225.47 LD+/- 2 minutes  departed
OH32020 OH342.06 LD  departed
OK42020 OK449.9 LD+/- 44 minutes  departed
OK52020 OK522.3 LD+/- 7.2667 hoursapproaching
OL12020 OL126.18 LD  departed
OL42020 OL49.50 LDapproaching
OM42020 OM415.77 LD  departed
OO12020 OO110.50 LD  departed Moon buzzer
OQ62020 OQ615.64 LD  departed
OR42020 OR426.47 LD  departed
OT12020 OT152.00 LD  departed
OU52020 OU514.25 LD  departed
OV42020 OV416.15 LD  departed
OW52020 OW514.00 LD+/- 2 minutes  departed
OX52020 OX58.20 LD  departed
OY42020 OY415.12 LD  departed intruder
OY52020 OY534.51 LD  departed
PA2020 PA3.62 LDoutbound intruder
VA1062015 VA10646.7 LD  distant
DateTfc.Time
3 Aug. '20Rept. Line
4 Aug. '20Rept. Line
5 Aug. '20Rept. Line
6 Aug. '20Rept. Line
7 Aug. '20Rept. Line
8 Aug. '20 Line
9 Aug. '20 Line

Object Details - Skychart objects presented in reverse designation order, newest first
  ("designation assigned to" indicates unofficial discovery credit)

2020 PA   -   outbound intruder
Approximate diameter6 meters (H=28.801)
Closest Earth approach0.15 LD at 0155 UTC on 1 Aug. 2020
Inside Earth-Moon system1329 on 31 July until 1420 UTC on 1 Aug. 2020
Inside Earth SOI30 July until 2 Aug. 2020
Inside ten LD of Earth26 July until 6 Aug. 2020
Closest Moon approach0.84 LD at 2353 UTC on 31 July 2020
Inside one LD of Moon1633 on 31 July until 0612 UTC on 1 Aug. 2020
Data based onJPL SSD orbit solution #1 downloaded from JPL on 3 Aug. 2020 UTC
based on 41 observations spanning one day
Optical observation  
Links  
2020 OQ6   -     departed
Approximate diameter21 meters (H=26.039)
Closest Earth approach1.09 LD at 0248 UTC on 31 July 2020
Inside Earth SOI30 to 31 July 2020
Inside ten LD of Earth29 July until 1 Aug. 2020
Closest Moon approach1.67 LD at 0629 UTC on 31 July 2020
Data based onJPL SSD orbit solution #2 downloaded from JPL on 2 Aug. 2020 UTC
based on 81 observations spanning one day
Optical observation  
  • reported from 17 observing codes during 1.6285 days: 104, 246, 595, A17, C77, E23, G34, H36, I41, J95, K38, K63, K87, L01, L18, X31, Z80
  • designation assigned to Zwicky Transient Facility observation at 0756 UTC 31 July 2020
  • last observed at 2301 UTC on 1 Aug. 2020 by Northolt Branch Obs.
Links  
2020 OA6   -   outbound
Approximate diameter21 meters (H=26.058)
Closest Earth approach6.35 LD at 2012 UTC on 4 Aug. 2020
Inside ten LD of Earth1 to 8 Aug. 2020
Data based onJPL SSD orbit solution #3 downloaded from JPL on 2 Aug. 2020 UTC
based on 40 observations spanning 11 days
Optical observation  
  • reported from 7 observing codes during 10.5176 days: 246, F52, G96, I52, J95, L01, N88
  • first observed at 1214 UTC on 22 July 2020 by Pan-STARRS 2
  • designation assigned to Mt. Lemmon Survey observation at 0644 UTC 30 July 2020
  • last observed at 0039 UTC on 2 Aug. 2020 by Great Shefford Obs.
NotesNHATS target
Links  
2020 OY5   -     departed
Approximate diameter64 meters (H=23.633)
Closest Earth approach9.03 LD at 0406 UTC on 26 July 2020
Inside ten LD of Earth25 to 27 July 2020
Data based onJPL SSD orbit solution #3 downloaded from JPL on 1 Aug. 2020 UTC
based on 70 observations spanning 4 days
Optical observation  
  • reported from 13 observing codes during 3.8093 days: 104, 160, 246, 595, 703, A17, F52, I52, K87, L18, T05, T08, V01
  • first observed at 1141 UTC on 28 July 2020 by Pan-STARRS 2
  • designation assigned to ATLAS Mauna Loa observation at 1057 UTC 29 July 2020
  • last observed at 0706 UTC on 1 Aug. 2020 by Steward Obs. Mt. Lemmon Station
Notesrisk
Links  
2020 OX5   -     departed
Approximate diameter14 meters (H=26.949)
Closest Earth approach6.75 LD at 1808 UTC on 31 July 2020
Inside ten LD of Earth28 July until 4 Aug. 2020
Data based onJPL SSD orbit solution #2 downloaded from JPL on 31 July 2020 UTC
based on 24 observations spanning 2 days
Optical observation  
  • reported from 6 observing codes during 1.6512 days: 104, F51, I93, J95, L01, U68
  • designation assigned to JPL SynTrack Robotic Telescope observation at 0824 UTC 29 July 2020
  • last observed at 0001 UTC on 31 July 2020 by Great Shefford Obs.
Notesrisk
Links  
2020 OW5   -     departed
Approximate diameter20 meters (H=26.138)
Closest Earth approach2.41 LD at 1806 UTC on 25 July 2020 - Note: JPL reports an approach uncertainty of +/- 2 minutes
Inside Earth SOIduring 25 July 2020
Inside ten LD of Earth19 to 31 July 2020
Data based onJPL SSD orbit solution #4 downloaded from JPL on 1 Aug. 2020 UTC
based on 36 observations spanning 3 days
Optical observation  
  • reported from 8 observing codes during 3.0581 days: 104, 204, G96, I52, I93, K63, K87, L01
  • designation assigned to Mt. Lemmon Survey observation at 0911 UTC 29 July 2020
  • last observed at 1035 UTC on 1 Aug. 2020 by Steward Obs. Mt. Lemmon Station
Links  
2020 OU5   -     departed
Approximate diameter37 meters (H=24.808)
Closest Earth approach9.28 LD at 1617 UTC on 29 July 2020
Inside ten LD of Earth28 to 31 July 2020
Data based onJPL SSD orbit solution #4 downloaded from JPL on 1 Aug. 2020 UTC
based on 90 observations spanning 3 days
Optical observation  
  • reported from 19 observing codes during 2.8194 days: 104, 160, 204, 246, 654, 958, A17, F51, G34, H21, I52, I93, J69, J95, K63, L01, L18, T05, U55
  • designation assigned to ATLAS Haleakala observation at 1051 UTC 28 July 2020
  • last observed at 0631 UTC on 31 July 2020 by Steward Obs. Mt. Lemmon Station
Links  
2020 OK5   -   approaching
Approximate diameter27 meters (H=25.512)
Closest Earth approach6.40 LD at 0734 UTC on 29 Oct. 2020 - Note: JPL reports an approach uncertainty of +/- 7.2667 hours
Inside ten LD of Earth26 Sept. until 30 Nov. 2020
Data based onJPL SSD orbit solution #3 downloaded from JPL on 1 Aug. 2020 UTC
based on 22 observations spanning 18 days
Optical observation  
  • reported from 3 observing codes during 18.2649 days: F51, K91, K93
  • first observed at 1327 UTC on 13 July 2020 by Pan-STARRS 1
  • designation assigned to Pan-STARRS 1 observation at 1106 UTC 18 July 2020
  • last observed at 1949 UTC on 31 July 2020 by LCO Sutherland A
NotesNHATS target
Links  
2020 OB5   -     departed
Approximate diameter11 meters (H=27.39)
Closest Earth approach6.22 LD at 2148 UTC on 18 July 2020 - Note: JPL reports an approach uncertainty of +/- 1.0167 hours
Inside ten LD of Earth15 to 22 July 2020
Data based onJPL SSD orbit solution #2 downloaded from JPL on 28 July 2020 UTC
based on 24 observations spanning one day
Optical observation  
  • reported from 4 observing codes during 1.1742 days: 474, G96, H21, I52
  • designation assigned to Mt. Lemmon Survey observation at 0710 UTC 26 July 2020
  • last observed at 1121 UTC on 27 July 2020 by Mt. John Obs.
Links  
2020 OY4   -     departed intruder
Approximate diameter3 meters (H=30.181)
Closest Earth approach0.11 LD at 0529 UTC on 28 July 2020
Inside Earth-Moon system2028 on 27 July until 1430 UTC on 28 July 2020
Inside Earth SOI27 to 29 July 2020
Inside ten LD of Earth24 July until 1 Aug. 2020
Closest Moon approach1.07 LD at 0502 UTC on 28 July 2020
Data based onJPL SSD orbit solution #4 downloaded from JPL on 31 July 2020 UTC
based on 68 observations spanning 2 days
Optical observation  
  • reported from 13 observing codes during 1.7635 days: 104, 204, 215, 474, G96, I93, J69, J95, K63, L01, L34, V06, Z84
  • designation assigned to Mt. Lemmon Survey observation at 0809 UTC 26 July 2020
  • last observed at 0229 UTC on 28 July 2020 by Great Shefford Obs.
NotesNHATS target
Links  
2020 OV4   -     departed
Approximate diameter12 meters (H=27.261)
Closest Earth approach8.48 LD at 1957 UTC on 17 July 2020
Inside ten LD of Earth11 to 24 July 2020
Data based onJPL SSD orbit solution #3 downloaded from JPL on 28 July 2020 UTC
based on 29 observations spanning 7 days
Optical observation  
  • reported from 8 observing codes during 6.8495 days: 033, 474, F51, F52, G96, H21, I52, L01
  • first observed at 1120 UTC on 20 July 2020 by Pan-STARRS 2
  • designation assigned to Mt. Lemmon Survey observation at 0952 UTC 26 July 2020
  • last observed at 0743 UTC on 27 July 2020 by ARO Westfield
NotesNHATS target
Links  
2020 OR4   -     departed
Approximate diameter25 meters (H=25.629)
Closest Earth approach1.19 LD at 2053 UTC on 28 July 2020
Inside Earth SOI28 to 29 July 2020
Inside ten LD of Earth26 to 30 July 2020
Closest Moon approach2.00 LD at 1941 UTC on 28 July 2020
Data based onJPL SSD orbit solution #2 downloaded from JPL on 27 July 2020 UTC
based on 37 observations spanning 6 days
Optical observation  
  • reported from 8 observing codes during 6.5405 days: 104, 474, F51, G96, I52, L01, L34, N88
  • first observed at 0934 UTC on 20 July 2020 by Pan-STARRS 1
  • designation assigned to Mt. Lemmon Survey observation at 0811 UTC 26 July 2020
  • last observed at 2233 UTC on 26 July 2020 by San Marcello Pistoiese Obs.
Notesrisk
Links  
2020 OM4   -     departed
Approximate diameter70 meters (H=23.434)
Closest Earth approach7.94 LD at 0049 UTC on 30 July 2020
Inside ten LD of Earth28 to 31 July 2020
Data based onJPL SSD orbit solution #5 downloaded from JPL on 1 Aug. 2020 UTC
based on 47 observations spanning 8 days
Optical observation  
  • reported from 11 observing codes during 7.6098 days: 160, 474, E23, E94, I52, J04, J95, K91, L18, T05, W88
  • designation assigned to ATLAS Haleakala observation at 1214 UTC 23 July 2020
  • last observed at 0252 UTC on 31 July 2020 by Castelmartini Obs.
Links  
2020 OL4   -   approaching
Approximate diameter37 meters (H=24.825)
Closest Earth approach9.50 LD at 1927 UTC on 8 Aug. 2020
Inside ten LD of Earth7 to 10 Aug. 2020
Data based onJPL SSD orbit solution #3 downloaded from JPL on 4 Aug. 2020 UTC
based on 26 observations spanning 11 days
Optical observation  
  • reported from 5 observing codes during 11.5274 days: 474, 568, F51, J04, K91
  • designation assigned to Pan-STARRS 1 observation at 1023 UTC 23 July 2020
  • last observed at 2302 UTC on 3 Aug. 2020 by LCO Sutherland A
Links  
2020 OK4   -     departed
Approximate diameter23 meters (H=25.824)
Closest Earth approach8.41 LD at 1743 UTC on 9 July 2020 - Note: JPL reports an approach uncertainty of +/- 44 minutes
Inside ten LD of Earth6 to 12 July 2020
Data based onJPL SSD orbit solution #1 downloaded from JPL on 26 July 2020 UTC
based on 15 observations spanning 3 days
Optical observation  
  • reported from 3 observing codes during 3.1306 days: 474, F51, J04
  • designation assigned to Pan-STARRS 1 observation at 0922 UTC 23 July 2020
  • last observed at 1230 UTC on 26 July 2020 by Mt. John Obs.
NotesNHATS target
Links  
2020 OH3   -     departed
Approximate diameter40 meters (H=24.629)
Closest Earth approach5.07 LD at 1105 UTC on 23 July 2020
Inside ten LD of Earth21 to 25 July 2020
Data based onJPL SSD orbit solution #1 downloaded from JPL on 24 July 2020 UTC
based on 43 observations spanning 2 days
Optical observation  
  • reported from 10 observing codes during 2.1519 days: 033, 204, 474, F51, I93, J04, J69, J95, T08, Z80
  • designation assigned to ATLAS Mauna Loa observation at 1323 UTC 22 July 2020
  • last observed at 1702 UTC on 24 July 2020 by Mt. John Obs.
Links  
2020 OG3   -   outbound
Approximate diameter15 meters (H=26.754)
Closest Earth approach7.09 LD at 2226 UTC on 4 Aug. 2020
Inside ten LD of Earth30 July until 10 Aug. 2020
Data based onJPL SSD orbit solution #7 downloaded from JPL on 31 July 2020 UTC
based on 31 observations spanning 8 days
Optical observation  
  • reported from 7 observing codes during 7.6704 days: 474, 568, F51, F52, I52, J04, K91
  • designation assigned to Pan-STARRS 1 observation at 1025 UTC 23 July 2020
  • last observed at 0231 UTC on 31 July 2020 by LCO Sutherland A
NotesNHATS target
Links  
2020 OH2   -     departed
Approximate diameter11 meters (H=27.458)
Closest Earth approach4.86 LD at 1208 UTC on 15 July 2020 - Note: JPL reports an approach uncertainty of +/- 2 minutes
Inside ten LD of Earth8 to 22 July 2020
Data based onJPL SSD orbit solution #3 downloaded from JPL on 26 July 2020 UTC
based on 17 observations spanning 4 days
Optical observation  
  • reported from 5 observing codes during 3.8779 days: 033, 568, F51, H36, V06
  • designation assigned to Pan-STARRS 1 observation at 1212 UTC 22 July 2020
  • last observed at 0917 UTC on 26 July 2020 by the Catalina Sky Survey Kuiper Telescope
NotesNHATS target
Links  
2020 OE2   -   outbound
Approximate diameter13 meters (H=27.044)
Closest Earth approach4.47 LD at 0304 UTC on 28 July 2020
Inside ten LD of Earth14 July until 11 Aug. 2020
Data based onJPL SSD orbit solution #8 downloaded from JPL on 31 July 2020 UTC
based on 72 observations spanning 10 days
Optical observation  
  • reported from 12 observing codes during 10.4683 days: 033, 104, 204, 246, A17, F51, I52, I93, J95, K87, T05, T08
  • first observed at 1236 UTC on 19 July 2020 by Pan-STARRS 1
  • designation assigned to ATLAS Mauna Loa observation at 1134 UTC 21 July 2020
  • last observed at 2351 UTC on 29 July 2020 by Guidestar Obs.
NotesNHATS target
Links  
2020 OT1   -     departed
Approximate diameter45 meters (H=24.377)
Closest Earth approach5.71 LD at 1721 UTC on 16 July 2020
Inside ten LD of Earth13 to 19 July 2020
Data based onJPL SSD orbit solution #7 downloaded from JPL on 31 July 2020 UTC
based on 63 observations spanning 12 days
Optical observation  
  • reported from 15 observing codes during 11.8270 days: 033, 104, A17, F52, G96, I52, I93, J95, K63, K87, L01, L34, T05, T08, V01
  • first observed at 1239 UTC on 18 July 2020 by Pan-STARRS 2
  • designation assigned to ATLAS Haleakala observation at 1306 UTC 21 July 2020
  • last observed at 0830 UTC on 30 July 2020 by the Mt. Lemmon Survey
Links  
2020 OO1   -     departed Moon buzzer
Approximate diameter18 meters (H=26.423)
Closest Earth approach1.74 LD at 1521 UTC on 27 July 2020
Inside Earth SOI26 to 28 July 2020
Inside ten LD of Earth21 July until 2 Aug. 2020
Closest Moon approach0.78 LD at 1543 UTC on 27 July 2020
Inside one LD of Moon0746-2339 UTC on 27 July 2020
Data based onJPL SSD orbit solution #9 downloaded from JPL on 31 July 2020 UTC
based on 123 observations spanning 7 days
Optical observation  
  • reported from 21 observing codes during 6.9159 days: 033, 104, 204, 474, 568, 673, C95, E23, F51, F65, G17, I93, J04, J95, K83, K92, K93, K96, L34, T08, T14
  • designation assigned to Pan-STARRS 1 observation at 0944 UTC 20 July 2020
  • last observed at 0743 UTC on 27 July 2020 by Mt. John Obs.
NotesNHATS target
Links  
2020 OL1   -     departed
Approximate diameter35 meters (H=24.915)
Closest Earth approach7.82 LD at 0307 UTC on 20 July 2020
Inside ten LD of Earth16 to 23 July 2020
Data based onJPL SSD orbit solution #8 downloaded from JPL on 29 July 2020 UTC
based on 144 observations spanning 9 days
Optical observation  
  • reported from 24 observing codes during 8.9629 days: 033, 104, 204, 595, 654, A17, C95, F51, I52, I93, J04, J69, J95, K38, K83, K87, K91, L01, L18, T05, T08, U71, V01, Z80
  • first observed at 1027 UTC on 20 July 2020 by Pan-STARRS 1
  • designation assigned to ATLAS Haleakala observation at 1108 UTC 20 July 2020
  • last observed at 0934 UTC on 29 July 2020 by Steward Obs. Mt. Lemmon Station
Links  
2020 OC1   -     departed
Approximate diameter18 meters (H=26.379)
Closest Earth approach9.56 LD at 1336 UTC on 31 July 2020
Inside ten LD of Earth28 July until 3 Aug. 2020
Data based onJPL SSD orbit solution #8 downloaded from JPL on 31 July 2020 UTC
based on 42 observations spanning 14 days
Optical observation  
  • reported from 8 observing codes during 13.7474 days: 033, 568, A17, F51, I52, J04, K91, L01
  • designation assigned to Pan-STARRS 1 observation at 1342 UTC 17 July 2020
  • last observed at 0739 UTC on 31 July 2020 by Steward Obs. Mt. Lemmon Station
NotesNHATS target
Links  
2020 OD   -     departed
Approximate diameter61 meters (H=23.738)
Closest Earth approach8.59 LD at 1248 UTC on 19 July 2020
Inside ten LD of Earth15 to 23 July 2020
Data based onJPL SSD orbit solution #14 downloaded from JPL on 4 Aug. 2020 UTC
based on 178 observations spanning 15 days
Optical observation  
  • reported from 29 observing codes during 14.9871 days: 130, 160, 246, 474, 595, 619, 654, 958, A17, G17, G96, H36, I52, I93, J69, J95, K38, K83, K87, L18, L34, L40, N88, Q62, T05, T08, U71, W34, Z80
  • designation assigned to ATLAS Mauna Loa observation at 1055 UTC 17 July 2020
  • last observed at 1036 UTC on 1 Aug. 2020 by ATLAS Mauna Loa
NotesNHATS target
Links  
2020 OC   -     departed
Approximate diameter15 meters (H=26.714)
Closest Earth approach3.56 LD at 1428 UTC on 13 July 2020
Inside ten LD of Earth5 to 21 July 2020
Data based onJPL SSD orbit solution #8 downloaded from JPL on 29 July 2020 UTC
based on 62 observations spanning 12 days
Optical observation  
  • reported from 8 observing codes during 11.7503 days: 033, 474, 654, F52, I52, K87, T05, T08
  • designation assigned to ATLAS Mauna Loa observation at 1122 UTC 17 July 2020
  • last observed at 0523 UTC on 29 July 2020 by Steward Obs. Mt. Lemmon Station
NotesNHATS target
Links  
2020 NZ   -     departed
Approximate diameter29 meters (H=25.31)
Closest Earth approach8.21 LD at 0053 UTC on 28 July 2020
Inside ten LD of Earth24 to 31 July 2020
Data based onJPL SSD orbit solution #5 downloaded from JPL on 28 July 2020 UTC
based on 26 observations spanning 14 days
Optical observation  
  • reported from 4 observing codes during 14.0586 days: 474, F51, H21, I52
  • designation assigned to Pan-STARRS 1 observation at 0710 UTC 13 July 2020
  • last observed at 0834 UTC on 27 July 2020 by Mt. John Obs.
Links  
2020 MX3   -     departed
Approximate diameter60 meters (H=23.771)
Closest Earth approach9.39 LD at 1639 UTC on 29 July 2020
Inside ten LD of Earth27 to 31 July 2020
Data based onJPL SSD orbit solution #20 downloaded from JPL on 6 Aug. 2020 UTC
based on 135 observations spanning 32 days
Optical observation  
  • reported from 22 observing codes during 32.4147 days: 104, 160, 204, 246, 474, 568, C77, F51, H45, I52, J69, J95, K38, K87, K91, K93, L18, L34, Q62, Q63, T05, T08
  • designation assigned to Pan-STARRS 1 observation at 1142 UTC 28 June 2020
  • last observed at 2140 UTC on 30 July 2020 by North Obs.
NotesNHATS target
Links  
2015 VA106   -     distant
Approximate diameter98 meters (H=22.7)
Closest Earth approach
Distance from Earth25.4 - 27.6 LD min-max during the observation period
Data based onJPL SSD orbit solution #26 downloaded from JPL on 4 Aug. 2020 UTC
based on 236 observations spanning 2015-2020
Optical observation  
  • reported from 5 observing codes during 3.3964 days: 033, I93, J95, L01, T08
  • first observed at 1126 UTC on 20 July 2020 by ATLAS Mauna Loa
  • last observed at 2056 UTC on 23 July 2020 by Schwarzschild Obs.
Notesprevious passage Nov. 2015 at 6.90 LD
Links  

Footnotes

Illustration of ten lunar distances.

1. Ten lunar distances:  One "lunar distance" (LD) is the average distance between Earth and Moon (about 384,400 km., the same as 238,855 miles or 9.59 times around Earth's equator). Ten lunar distances has no special astronomical importance but is a useful giant traveling "bubble" within which to organize this special reporting. The approach of a small Solar-System body becomes more interesting when it nears or comes closer than 2.41 LD, as it encounters our planet's gravitational sphere of influence ( SOI). Earth's gravity can change the orbits of objects passing through its SOI. The Moon also has its own SOI, which changes as its distance from Earth varies, but never extends much more than 0.18 LD. (The simple illustration above, with Earth and Moon not to scale, shows the Earth SOI as a dotted vertical blue line.) The "Earth-Moon system" is generally defined as that region of space within a radius of one lunar distance from Earth, so an object can pass quite close to the Moon yet not be described as coming "inside" the E-M system.

2. Data credit:  All data on this page derived from orbit solutions comes from the NASA JPL Solar System Dynamics (SSD) Group through its Horizons system. All information about optical observations comes from the IAU Minor Planet Center (MPC) and info about radar observations comes from JPL SSD. The MPC, NASA, and JPL are not associated with this page or A/CC, and responsibility for the interpretation of this information and its use here rests entirely with A/CC. Important note: Approach times presented here as to-the-minute may have unstated uncertainties of a few minutes, or many minutes or even hours for objects with old or very short observation spans, which is significant because the Earth moves through its own diameter in about seven minutes. Thus actual encounter distances may vary, occasionally by as much as ten lunar distances. See JPL's Close Approach Tables for nominal vs. minimum possible passage distances and times, and for their note about uncertainties.

3. Size estimates:  Object diameters are rough approximations derived by standard formula from H, an object's "absolute magnitude" (brightness), where higher numbers represent dimmer (thus usually smaller) objects.