| Progress 31 | |
| Mission Type: | Mir resupply |
| Cospar Id: | 1987-066A |
| Satcat: | 18283[1] |
| Spacecraft: | Progress (No.138) |
| Spacecraft Type: | Progress 7K-TG[2] |
| Manufacturer: | NPO Energia |
| Launch Date: | 3 August 1987, 20:44:11 UTC |
| Launch Rocket: | Soyuz-U2 |
| Launch Site: | Baikonur, Site 1/5 |
| Docking: | |
| Disposal Type: | Deorbited |
| Decay Date: | 23 September 1987, 00:22:00 UTC |
| Orbit Epoch: | 3 August 1987 |
| Orbit Reference: | Geocentric |
| Orbit Regime: | Low Earth |
| Orbit Periapsis: | 187 km |
| Orbit Apoapsis: | 250 km |
| Orbit Inclination: | 51.6° |
| Orbit Period: | 88.9 minutes |
| Apsis: | gee |
| Programme: | Progress (spacecraft) |
| Previous Mission: | Progress 30 |
| Next Mission: | Progress 32 |
Progress 31 was a Soviet uncrewed Progress cargo spacecraft, which was launched in August 1987 to resupply the Mir space station.
Progress 31 launched on 3 August 1987 from the Baikonur Cosmodrome in the Kazakh SSR. It used a Soyuz-U2 rocket.[4]
Progress 31 docked with the aft port of the Kvant-1 module of Mir on 5 August 1987 at 22:27:35 UTC, and was undocked on 21 September 1987 at 23:57:41 UTC.[5]
It remained in orbit until 23 September 1987, when it was deorbited. The deorbit burn occurred at 00:22:00 UTC and the mission ended at 01:02 UTC.