| R-S | Reed-Solomon |
| R/T | Receive/Transmit |
| R&D | Research and Development |
| R&M | Reliability and Maintainability |
| R&OM | Risk and Opportunity Management |
| R&R | Remove and Replace |
| R&R | Restrain and Release |
| R1 | Release 1 |
| R2 | Release 2 |
| RA | Registration Authority |
| RA | Requirements Analysis |
| RAC | Real Application Cluster |
| RAC | Risk Assessment Classification |
| RAD | Resource Allocation Document |
| RADIUS | Remote Authentication Dial In User Service |
| RaFTR | Resample and Format, Timed Release |
| RAL | Reverberant Acoustics Laboratory |
| RAM | Random Access Memory |
| RAM | Resource Allocation Matrix |
| RAM | Requirements Allocation Matrix |
| RAM | Responsibility Assignment Matric |
| RAMMB | Regional and Mesoscale Meteorology Branch (NESDIS) |
| RAOB | Radiosonde Observation |
| RAP | Regional Analysis and Prediction |
| RAS | Reliability, Availability, and Serviceability |
| RATS | Request for Action Tracking System |
| RB | Radiation Budget |
| RBAC | Role-Based Access Control |
| RBCA | Risk-Based Cost Analysis |
| RBDA | Risk-Based Decision Assessment |
| RBS | Resource Breakdown Structure |
| RBSA | Risk-Based Schedule Analysis |
| RBU | Remote Backup station |
| RCA | Request for Corrective Action |
| RCCPA | Root Cause Corrective Action and Preventive Action |
| RCM | Reliability Centered Maintenance |
| RCP | Right Circular Polarized |
| RCVR | Receiver |
| RCWG | Requirements Control Working Group |
| RD | Restricted Data |
| RDBMS | Relational Database Management System |
| RDC | Relay Driver Card |
| RDDP | Reliable Dissemination Data Protocol (LM-KO) |
| RDL | Raw Data Link |
| RDM | Radiation Dose Margin |
| RDM | Raw Data Modulator |
| RDR | Raw Data Recorder |
| RDR | Ryco Development and Research |
| RDW | Request for Deviation or Waiver |
| RE | Radiated Emissions |
| RE | Radiation Engineer |
| RE | Recurring Engineering |
| REA | Rocket Engine Assembly |
| REALM | Regional East Atmospheric Lidar Mesonet |
| REC | Record of Environmental Consideration |
| REMB | Resource and Engineering Management Board |
| REQM | Requirements Management |
| REST | REpresentational State Transfer |
| RF | Radio Frequency |
| RFA | Request For Action |
| RFC | Request For Change |
| RFC | Request for Comments |
| RFC | River Forecast Centers |
| RFCT | Radio Frequency Compatibility Test |
| RFCTWG | Radio Frequency Compatibility Test Working Group |
| RFI | Radio Frequency Interference |
| RFID | Radio Frequency Identification |
| RFMFT | Relative Four Minus Five Test (cloud detection test) |
| RFP | Request For Proposal |
| RFQ | Request for Quotation |
| RFTE | RF Test Equipment |
| RGB | Red Green Blue |
| RGCT | Reflectance Gross Contrast Test |
| RH | Relative Humidity |
| RHCP | Right-Hand Circular Polarization |
| RHEL | Red Hat Enterprise Linux |
| RHEV | Red Hat Enterprise Virtualization |
| RHEV-H | Red Hat Enterprise Virtualization -Hypervisor |
| RHEV-M | Red Hat Enterprise Virtualization -Manager |
| RHN | Red Hat Network |
| RIDM | Risk-Informed Decision-Making |
| RIS | Risk Information Sheet |
| RISTM | Reduced Integrated Satellite (or Spacecraft) Thermal Model |
| RIU | Remote Interface Unit |
| RLAT | Radiation Lot Acceptance Test |
| RM | Reliability Manager |
| RM | Requirements Management |
| RM | Risk Manager |
| RM | Risk Management |
| RMA | Reliability, Maintainability, and Availability |
| RMAN | Recovery Manager |
| RMAP | Remote Memory Access Protocol |
| RMAPP | Reliability Maintainability Availability Program Plan |
| RMB | Risk Management Board |
| RMC | Redundancy Management Card |
| RMI | Ranging Mode Index |
| RMIS | Risk Management Information System |
| RMM | Radiometric Math Model |
| RMM | Release Mission Management |
| RMMU | Release Mission Management Update |
| RMON | Remote Network Monitoring |
| RMP | Requirements Management Plan |
| RMP | Risk Management Plan |
| RMs | Records Managers (Program) |
| RMS | Research Microwave System |
| RMS | Requirements Management System |
| RMS | Resources Management System |
| RMS | Root Mean Square |
| RMSE | Root Mean Square Error |
| RMT | Resource Modeling Tool (part of MMM) |
| RMW | Radius of Maximum Wind |
| RO | Risk Owner |
| ROA | Return on Assets |
| ROI | Return On Investment |
| ROIC | Read Out Integrated Circuit |
| ROLO | RObotic Lunar Observatory |
| ROM | Read Only Memory |
| ROM | Rough Order of Magnitude (Ground) |
| ROMB | Risk/Opportunity Management Board |
| ROMT | Risk/Opportunity Management Team |
| ROP | Recommended Operating Procedure |
| RPIE | Real Property Installed Equipment |
| RPM | Redhat Package Manager |
| RPM | Replacement Product Monitor |
| RPO | Recovery Point Objective |
| RPP | Reliability Program Plan |
| RPT | Report |
| RR | Rainfall Rate |
| RRB | Risk Review Board |
| RRCC | Rainfall Rate per Cubic Centimeter |
| RRPE | Rainfall Rate Precipitation Estimate |
| RRR | Release Readiness Review |
| RRT | Risk Reduction Testing |
| RS FEC | Reed Solomon Forward Error Correction |
| RSA | Rational Software Architect |
| RSM | Rational Software Modeler |
| RSMC | Regional Specialized Meteorological Center |
| RSR | Reflected Shortwave Radiation |
| RSS | Range Safety System |
| RSS | root sum square |
| RT | Radiative Transfer |
| RT | Real-time |
| RTCS | Relative Time Command Sequence |
| RTCT | Relative Thermal Contrast Test (cloud detection test) |
| RTD | Resistance Temperature Detector |
| RTEMS | Remote Tivoli Enterprise Management Server |
| RTEP | Real-Time Event Processor |
| RTG | Real Time Global |
| RTG_SSG | Real Time Global Sea Surface Temperature |
| RTL | Risk Tracking Log |
| RTM | Radiative Transfer Model |
| RTM | Reduced Thermal Model |
| RTM | Requirements Traceability Matrix |
| RTO | Ready To Operate |
| RTO | Recovery Time Objective |
| RTOFS | Real Time Ocean Forecast System |
| RTOS | Real-Time Operating System |
| RTP | Re-engineered Test Program |
| RTS | Relative Time Sequence |
| RTTOV | Radiative Transfer for TIROS Operational Vertical Sounder |
| RTVM | Requirements Traceability and Verification Matrix |
| RUC | Rapid Update Cycle |
| RUT | Reflectance (0.63 mm) Uniformity Test |
| RVCT | Relative Visible Contrast Test |
| RVM | Requirements Verification Matrix |
| RVS | Raytheon Vision Systems |
| RVT | Release Verification Test |
| RVTM | Requirements Verification Traceability Matrix |
| RW | Rolling Wave |
| RWA | Reaction Wheel Assembly |
| RX | Receiver |