Status Report

ISS On-Orbit Status 27 Feb 2002

By SpaceRef Editor
February 27, 2002
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All ISS systems continue to function nominally, except as noted previously or below.

Early this morning, ISS suffered a computer failure in the U.S. segment (USOS). C&C3 MDM (command & control computer #3), in primary position, switched itself to Diagnostic mode when encountering a newly uploaded power control (“load shed”) routine, called a PPL (prepositioned load). While part of the new R2 (release 2) software upgrade, the PPL apparently still contained some R1 features, either in an address or file command, which was not (any longer) recognized by the S-band system’s R2 software. Automatically, C&C1, the backup computer, transitioned to prime (with C&C2 becoming backup and C&C3 standby) but it also aborted operations, and C&C1 became prime (C&C2 backup, C&C3 standby). When control and S-band function was lost, U.S. motion control authority automatically transferred from the second-tier GNC (guidance, navigation & control) MDM to the Russian motion control system. Without the GNC, Ku-band was also lost, as was S-band HDR (high data rate), but flight controllers were able to switch S-band to its LDR (low data rate) link, regaining communications with onboard systems. Analysis of downlinked data dumps got underway, but the C&C MDMs are up and running, and the ISS was moded from RS thruster control to free drift while ground specialists work to verify their full functionality and to reestablish nominal conditions under CMG control.

Due to the C&C computer incident, the “Robotics Day #2” activities, aimed mostly at familiarizing the crew with SSRMS ops and first run of its new R2 software, are being rescheduled from today to some time next week.

CDR Yuri Onufrienko completed cable inspection and voltage continuity testing on the SNT-23 voltage and current stabilizers in the SM electrical power system. He had already done some troubleshooting on the connections on 2/8 when the SNT-23 system had indicated a short, which showed itself by tripping an RPCM (remote power controller module) in the Node. [The SNTs are designed to accept “external” power from the ARCUs (American-to-Russian converter units) when an acute shortage arises and a specific number ofÊ storage batteries have already been discharged. The units are located under the TVIS but can be accessed from the side through a panel without having to remove the treadmill. The four SNTs are capable of transferring power at up to 1.5 kW each, with an input voltage on these stabilizers variable between 100-180 V.]

FE-1 Carl Walz collected potable water samples for in-flight chemical and microbial testing, using the WMK (water microbiology kit), which detects and enumerates microorganisms in the onboard water systems. [WMK consists of a syringe pump assembly, microbial capture devices, air filter assemblies, liquid media, and sample and waste bags. After collection, water samples are drawn through the microbial capture device, which filters the water and captures microorganisms. Data from the WMK data includes total count (colony forming units) and fecal coliforms. Results are read at two and five days after inoculation of the microbial capture device (Petri dishes).]

FE-2 Dan Bursch meanwhile performed fluid sampling on the ITCS (internal thermal control system) coolant, using the WMK.

Onufrienko again operated the TEPC (tissue equivalent proportional counter) radiation instrument by power-cycling it, required every time after the grofƒ-has commanded the instrument on Mondays, Wednesdays and Fridays for radiation readings. He also completed the regular daily maintenance tasks on SOSH (life support systems), IMS delta file preparation and switching the BMP absorption bed #2 from regeneration cycle to purification mode, joining filter channel #1.

CDR replaced three IPK-1 gas masks in the FGB with fresh units and stowed the old masks. He also ran a checkout of the Russian MedOps GAMMA-1M arterial blood pressure unit, for which he placed a blood pressure cuff on his left upper arm and had it pumped up to 180 mmHg for taking readings, with real-time downlink to Russian ground stations (RGS).

Analysis of the TVIS treadmill power failure yesterday showed that the circuit breaker (fuse) of the TVIS motor tripped when the power drawn exceeded a certain preset limit setting. TVIS is designed as a power-sharing device; total current (amps) is shared between the motor current draw, the stabilization system, and other TVIS components. If the stabilization system requires more power to provide additional stabilization, then power is taken from the motor drive, resulting in a decrease in motor speed. Since it appears that speeds above 6 mph may cause power sharing to exceed preset limits, the crew was asked to reactivate the TVIS but run at slower speeds while data are being gathered for further determination. This restriction does not apply to non-motorized treadmill mode.

The crew did not yet exercise on TVIS today, pending Russian concurrence in the above conclusions, but they worked out on RED (resistive exercise device) and CEVIS (cycle ergometer with vibration isolation). [RED prevents muscle atrophy of the major muscle groups (legs, hips, trunk, shoulders, arms and wrists) by maintaining strength, power, and endurance. There are over a dozen different anaerobic exercises that can be performed with RED. CEVIS is used for systemic aerobic conditioning and can be applied to independent upper and lower limb activity. As with the TVIS, its vibration isolation system counteracts (isolates) translations in x, y, and z, as well as roll, pitch and yaw.]

Solar Beta angle continues to decrease. [This will improve conditions for the station. Beta is defined as the angle between the orbital plane and the Ecliptic (Earth orbit plane) or the Earth-Sun line. Because the ISS has no “alpha” gimbals yet (until Flight 12A), the solar arrays cannot be oriented to the Sun at high Betas to meet power generation requirements unless the station abandons the nominal LVLH (local vertical/local horizontal attitude, with the “belly” of ISS always facing Earth) and flies in the quasi-solar inertial attitude called XPOP (x-axis perpendicular to orbital plane), as it does at present. These conditions, however, have disadvantages for the ISS in terms of communication coverage (reduced), thermal heating (higher) and microgravity (because thrusters may be required more often).]

Today’s target areas for CEO (crew earth observations) were E. Mediterranean Dust and Smog (weak high pressure persists over the eastern Mediterranean basin. Of interest: oblique views to the right of track, especially over Greece and the Aegean Sea to document aerosol distribution), Nile River Delta (with key features to the right of track this pass, crew was to try for oblique regional, context views of the Nile Delta), W. Mediterranean Dust and Smog (with an Atlantic storm approaching Spain from the SW on this pass, crew was asked to look well to the right of track toward Algeria and Morocco for blowing dust), Gulf of St. Lawrence (most of the Gulf of St Lawrence passed to the right of track on this pass. Of interest: oblique, context views of ice pack coverage northeastward towards the Strait of Belle Isle).

ISS Orbit (as of this morning, 6:57am EST):

  • Mean altitude — 383.9 km
  • Apogee — 391.3 km
  • Perigee — 376.4 km
  • Period — 92.2 min.
  • Inclination (to Equator) — 51.64 deg
  • Eccentricity — 0.0010998
  • Orbits per 24-hr. day — 15.61
  • Altitude decrease — 310 m (mean) in last 24 hours
  • Solar Beta Angle: -59.3 deg (magnitude decreasing)
  • Revolutions since FGB/Zarya launch (Nov. ’98) — 18692
  • Current Flight Attitude — XPOP (x-axis perpendicular to orbit plane [yaw: ~0 deg, pitch: 5 deg., roll: 0 deg])

For more on ISS orbit and naked-eye visibility dates/times, see


SpaceRef staff editor.