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Magellan Status 4/17/91 MAGELLAN STATUS REPORT April 17, 1991 The Magellan spacecraft and its radar system are performing well. Five star calibrations Tuesday were fully successful, with two partially successful. The attitude updates still average less than .02 degree. The spacecraft is now performing momentum wheel desaturations on every other orbit and star calibrations every orbit. The weekly command sequence was successfully set to Magellan late Tuesday and is now being executed. This new mapping sequence includes two eight-minute "hide" periods in each three hour and 15-minute orbit. During that period the spacecraft is shaded by the high-gain antenna for thermal control. The maneuver is necessary because the geometry of the planets in relation to the sun places the spacecraft in direct sunlight for too long a period of time. As of this report, there has only been one orbit with the hide sequences and there appears to be a cooling trend. The hide periods will increase from now through the end of the primary mission May 15. Next week, for example, there will be two 12-minute hide periods in each orbit which will cut the 37.2- minute mapping swath by 4.5 minutes. In the following weeks, the hide periods increase to 23 minutes, which will cut mapping by 10 minutes, and then 36 minutes of hide period which will cut mapping by 15 minutes. _____ AJS 4-17-91 9:00 AM MAGELLAN STATUS REPORT 1. The Magellan spacecraft and its radar system are performing nominally. 2. Five the STARCALS yesterday were fully successful, with two partially successful. The attitude updates still average less than .02 degree. The spacecraft is now performing DESATS on every other orbit and STARCALS every orbit. 3. The weekly command sequence M1107 was successfully sent to Magellan along with the radar control parameter and mapping quaternion files, and is now executing. As of this report time, we have seen only one orbit of the "Two- Hide" sequence, and there appears to be a definite cooling trend. ___________________ AJS (pca) 4/17/91 MAGELLAN SPECIAL REPORT SCIENCE DATA PRODUCTS During the primary mission, the Project has frequently reported on the number of mapping orbits completed and the orbits for which data was successfully transmitted to the earth. The ultimate measure of mission success, however, is the production and distribution of final scientific data products. End-to-End Data Flow The flow of data from the radar sensor onto the spacecraft tape recorder, its transmission to Earth where it is again recorded on tape as Original Data Records (ODRs), the conversion of ODRs to Experiment Data Records (EDRs), then into Full-Resolution Basic Image Data Records (F-BIDR's) and various mosaics (F-MIDRs, C1-MIDRs, etc) is one of the major challenges of the Magellan mission. 1. The radar sensor transmits bursts of radar pulses toward the surface of Venus. A portion of each radar echo is quantized to generate 16-bit data samples at a rate pf 2.26 x 106 samples per second. These are compressed by the Block Adaptive Quantizer to reduce the bits-per-sample from 16 to 4. The data acquired during each burst of pulses is stored in a buffer memory and then sent to the spacecraft tape recorder at a uniform rate of 800 kbps for each 37.2 minute mapping pass. Thus, Magellan produces 1.8 x 109 bits per orbit. 2. The spacecraft tape recorder is played back at a 268.8 kbps rate and transmitted via an X-band communication link to the Deep Space Tracking stations, where the data is recorded on standard computer-compatible, 3/4 inch magnetic tapes at a recording density of 6,250 bytes/inch. The data from each orbit normally requires two 2400 foot reels of tape. These tapes are called Original Data Records (ODRs). 3. During the first mission cycle, the ODRs from Goldstone are driven into JPL daily. ODRs at the Madrid and Canberra stations are collected for one week then flown to JPL. Although these ODRs can take as much as 21 days to reach JPL, the current backlog is about 12 days. 4. Processing of data tapes is coordinated by Magellan's Data Management and Archive Team (DMAT) which schedules each stage of data processing from ODRs to EDRs to various image products. DMAT also catalogs and stores the data tapes. 5. ODR tapes are logged by DMAT and delivered to the Magellan High Rate (MHR) processor where the station overlap is removed, and ancillary data needed for further processing and user information is added to produce the Experiment Data Records (EDRs). 6. EDRs are then logged by DMAT and forwarded to the SAR Data Processing Subsystem (SDPS) in Building 300. SDPS operates on a two eight hour shift basis, Monday through Friday. Here the 1.8 x 109 bits per orbit of raw radar data from each SARvEDR is converted into 0.8 x 109 bits of image data for each orbit and combined with ancillary data to form Full Resolution Basic Image Data Record tapes (F- BIDRs). F-BIDRs contain the long thin strips of orbit image data which cover an area on Venus approximately 12 miles wide and 10,000 miles long (20 by 17,000 KM). Understandably, these are called "radar noodles". 7. As a check of the data quality and interpretability, the F-BIDRs are also delivered as long thermal prints to the science work area. On each print the "noodle" is presented in four parallel pieces approximately 1 inch wide by 15 feet long. 8. The F-BIDRs are transmitted electronically to the Image Data Processing Subsystem, (IDPS) in Building 168 to connect the digital form of these thin image strips into Mosaicked Image Data Record (MIDR) products: a. F-MIDRs: The highest resolution image mosaics are the Full-resolution MIDRs. These are images of 300 x 340 mile (500 x 532 KM) areas of the Venus surface with a pixel spacing of 75 meters. F-MIDRs will be produced for about 15% of the total surface area. b. C1-MIDRs: These mosaicked products compress the full resolution pixel data by averaging each 3 x 3 array into a single pixel value. Each frame covers an area on Venus measuring approximately 900 x 1000 miles (1450 x 1600 KM). c. C2 & C3-MIDRs: These products further compress the pixel arrays by averaging 9 x 9 and 27 x 27 arrays of full resolution data. The C2 frames cover 45 degrees of latitude, and 45 to 72 degrees of longitude. The C3 frames cover 80 degrees of latitude by 120 degrees of longitude. All of the surface of Venus can be displayed in six C3MIDRs. d. PIDRs: These are Polar Image Data Records, specifically designed for the polar areas of the planet. They contain portions of adjacent F-BIDRs covering the area from 80x latitude to the North Pole. 9. In addition to the image data record products, altimetry and radiometry data products are being produced by investigators at the Massachusetts Institute of Technology. These include: a. ARCDRs - Altimeter/Radiometer Composite Data Records b. GTDRs - Global Topographic Data Records c. GSDRs - Global Slope Data Records d. GEDRs - Global Emissivity Data Records e. GREDRs - Global Reflectivity Data Records 10. CD-ROMs: Many science data products end up as images, either printed as photos or distributed as digital records. Many of the science investigators need the digital records because there are many analysis tools which can be applied to this computer-readable form of the images. It is the Project's plan to distribute the images to the science community in the form of CD-ROM = Compact Disk - Read Only Memory compact disks (CD- ROMs). The first of these CD-ROMs was made available on March 8, 1991, and contained ten full resolution mosaicks from the first 24 orbits, i.e. the first 3 days of mapping. The second CD-ROM includes mosaicks from the first 21 days of mapping is scheduled for release to the science community on April 19, 1991. The third CD-ROM, containing full resolution mosaicks beyond the first 21 days, is being used to test the production system for CD-ROMs and will not be distributed until about mid-summer. Work is proceeding, however, on CD-ROMs 4, 5 and 6, containing images from the first 21 days of mapping. The goal is to release these about May 17. The Project is preparing for the production of 50-60 CD-ROMs in the remainder of calendar 1991, including images from all of Cycle 1, on a schedule of about two per week. CD-ROMs will also be used to distribute these other science data records. The first Altimeter/Radiometer Composite Data Record disk is scheduled for production, starting in late April, with release to the science community in June. 11. Perhaps the most striking visual form of the data are the simulated flights over the surface of Venus produced frame by frame by combining the Magellan image and altimeter data. Videos of 2,000 to 5,000 mile flights over and around significant surface features will be produced every three months. (This process is itself a unique story and will be described in a future special report.) Development of the Magellan Data Processing System Due to budget constraints, the completion of Magellan processing system was deferred until after launch. Throughout cruise, final software development and test and system integration and test were accomplished, targeted for completion by May 1990. This represented a major development challenge in addition to operating the Spacecraft. While most of the system was in place by May 1991, certain software builds took most of the summer to complete, but were ready for mapping operations prior to arrival at Venus. The Magellan processing challenge for a planetary mission is unique and quite large. The Magellan system is required to process one week of acquired data in one week --- the highest rate and the longest duration for any planetary mission. Previous planetary encounters consisted of intense near encounter phases lasting for a few months, over which large volumes of data are collected, followed by many months of quieter cruise activities. Magellan's "Near Encounter" Magellan continues in an intensive "near encounter" phase for 243 days, the time it takes the planet to rotate once underneath the spacecraft. During this time, data are collected on each 3.25 hour orbit, 24 hours a day, 7 days a week. In seven months Magellan collected more data bits than all the Mariners, Vikings and Voyagers. At the end of the primary mission, the "near encounter" continues into the next 243-day cycle, then the next and the next. At the start of mapping on 15 September, the data processing system began to immediately produce high quality data products. The first three weeks of radar data processing operations concentrated on engineering refinements, performance tests, and special product generation to support initial press conferences. The standard data processing activity started on October 9th. Several refinements were made to correct problems that have been discovered during operations. The malfunction of one of the spacecraft tape recorders resulted in several modifications to data processing to alleviate the effects of the resulting damage in the received radar data. The recent experience indicates that the planned Cycle 1 data products will all be completed by the original schedule date of June 28, 1991. SPACELINK NOTE: For information on obtaining the CD-ROM disk, contact: National Space Science Data Center NASA/Goddard Space Flight Center Code 633 Greenbelt, MD 20771 301/286-6695