A320 captain reported an near midair collision with another aircraft in the vicinity of pdx airport.

Attributes
ACN	1597463
Time
Date	201811
Local Time Of Day	0001-0600
Place
Locale Reference	PDX.Airport
State Reference	OR
Environment
Flight Conditions	IMC
Aircraft 1
Make Model Name	A320
Operating Under FAR Part	Part 121
Flight Phase	Descent
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	Descent
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument Flight Crew Multiengine
Events
Anomaly	ATC Issue All Types Conflict NMAC

Narrative:

We were at assigned altitude of 13;000 ft. An aircraft began a fast descent towards us. At 500 ft away from us; we got an RA to climb. We began a climbing/ fairly steep turn to miss him. It was close enough that we saw his lights even though IMC. After calling ATC on the ground; we were told that he was given an approach clearance into a satellite airport. This should not have happened.

Original NASA ASRS Text

Title: A320 Captain reported an NMAC with another aircraft in the vicinity of PDX airport.

Narrative: We were at assigned altitude of 13;000 FT. An aircraft began a fast descent towards us. At 500 FT away from us; we got an RA to climb. We began a climbing/ fairly steep turn to miss him. It was close enough that we saw his lights even though IMC. After calling ATC on the ground; we were told that he was given an approach clearance into a satellite airport. This should not have happened.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.