Vapor　compression　heat　pump　is　a　new　concept　of　thermal　control　system　and　refrigerator　for　future　space　use.　Compressor　is　a　key　component　in　the　vapor　compression　heat　pump.　Development　of　compressor　capable　of　operating　in　both　microgravity　(10　E-6　g)　and　lunar　(1/6　g)　environments　is　urgently　needed　for　space　thermal　control　systems　based　on　heat　pump　technique.　In　this　paper,　a　miniature　rotary　compressor　by　ASPEN　company　was　modified　to　realize　acceptable　compressor　lubrication　and　oil　circulation　in　microgravity　environments.　An　experimental　system　was　built　up　to　check　the　performance　of　the　modified　compressor　subjected　to　microgravity.　A　performances　comparison　of　inverted　compressor　with　upright　one　was　made.　The　influences　of　operating　parameters　such　as　refrigerant　charge,　cooling　water　temperature　as　well　as　compressor　speed　on　the　performances　of　vapor　compression　heat　pump　were　investigated.　The　results　show　that　the　modified　miniature　rotary　compressor　in　inverted　mode　can　operate　stably　in　a　long　period,　which　indicates　that　the　modified　compressor　can　be　employed　in　microgravity　environments.　Compressor　discharge　temperature　increased　or　decreased　while　COP　changed　more　obviously　with　cooling　water　temperature　and　speed　in　microgravity.　In　most　cases,　performance　of　the　upright　compressor　is　superior　to　that　of　the　inverted　one.　But　when　the　compressor　speed　is　from　1500　rpm　to　2500　rpm　or　the　coolant　temperature　is　between　20　and　25　degrees,　the　performance　of　inverted　compressor　is　better.　The　highest　discharge　temperature　of　the　inverted　compressor　can　be　as　high　as　1.7　times　that　of　the　upright　one.　The　maximum　of　heating　COP　and　cooling　COP　of　upright　compressor　is　respectively　1.21　and　1.16　times　that　of　inverted　compressor.　The　study　of　modified　miniature　rotary　compressor　on　gravity-independence　provides　an　experimental　basis　and　lays　foundation　for　space　applications.　(C)　2015　Elsevier　Ltd.　All　rights　reserved.