SECURITIES AND EXCHANGE COMMISSION
                            Washington, D.C. 20549
                               ________________
                               SCHEDULE 14D-1/A

                  Tender Offer Statement Pursuant to Section
                14(d)(1) of the Securities Exchange Act of 1934
                              (Amendment No. 12)
                              __________________
                              COMSAT CORPORATION
                           (Name of Subject Company)

                                 REGULUS, LLC
                          LOCKHEED MARTIN CORPORATION
                                   (Bidders)

                        Common Stock, Without Par Value
                        (Title of Class of Securities)

                                   20564D107
                     (CUSIP Number of Class of Securities)

                            STEPHEN M. PIPER, ESQ.
                          LOCKHEED MARTIN CORPORATION
                             6801 ROCKLEDGE DRIVE
                           BETHESDA, MARYLAND 20817
                                (301) 897-6000
                 (Name, Address and Telephone Number of Person
    Authorized to Receive Notices and Communications on behalf of Bidders)

                                   COPY TO:
                              DAVID G. LITT, ESQ.
                             O'MELVENY & MYERS LLP
                             555 13TH STREET, N.W.
                                SUITE 500 WEST
                         WASHINGTON, D.C.  20004-1109
                                (202) 383-5300

                           CALCULATION OF FILING FEE

Transaction Valuation(1): $1,169,509,386   Amount of Filing Fee: $233,901

(1)  Estimated for purposes of calculating the amount of the filing fee only.
     The amount assumes the purchase of 25,703,503 shares of common stock,
     without par


     value (the "Shares"), of COMSAT Corporation (the "Company") at a price per
     Share of $45.50 in cash (the "Offer Price"). Such number of shares
     represents 49% of the shares of Common Stock of the Company outstanding as
     of September 11, 1998, minus the number of shares of the Series II Common
     Stock of the Company outstanding as of September 11, 1998.

[x]  Check box if any part of the fee is offset as provided by Rule 0-11(a)(2)
     and identify the filing with which the offsetting fee was previously paid.
     Identify the previous filing by registration statement number, or the form
     or schedule and the date of its filing.

Amount previously paid: $233,901   Filing Parties:  Regulus, LLC and
                                                    Lockheed Martin Corporation

Form or registration no.:  Schedule 14D-1     Date Filed: September 25, 1998

                        (Continued on following page(s))

                                 (Page 2 of 8 pages)


     This Amendment No. 12 to the Tender Offer Statement on Schedule 14D-1 (the
"Schedule 14D-1") amends and supplements the Schedule 14D-1 of Regulus, LLC, a
single member Delaware limited liability company (the "Purchaser") and a wholly-
owned subsidiary of Lockheed Martin Corporation, a Maryland corporation
("Parent"), in respect of the tender offer (the "Offer") by the Purchaser to
purchase up to 49% (less certain adjustments) of the issued and outstanding
shares (the "Shares") of common stock, without par value, of COMSAT Corporation,
a District of Columbia corporation (the "Company"), at a price of $45.50 per
Share, net to the seller in cash, without interest thereon, upon the terms and
subject to the conditions set forth in the Offer to Purchase dated September 25,
1998 (the "Offer to Purchase") and in the related Letter of Transmittal.  The
Offer is being made pursuant to an Agreement and Plan of Merger dated as of
September 18, 1998, among the Company, Parent and Deneb Corporation, a wholly-
owned subsidiary of Parent.  The Schedule 14D-1 was initially filed with the
Securities and Exchange Commission on September 25, 1998.  Capitalized terms not
defined herein have the meanings assigned thereto in the Schedule 14D-1 and the
Offer to Purchase, which is attached as Exhibit (a)(1) to the Schedule 14D-1.

     The Purchaser and Parent hereby amend and supplement the Schedule 14D-1 as
follows:

ITEM 10:  ADDITIONAL INFORMATION

     Item 10(b) is hereby amended and supplemented by the addition of the
following paragraphs thereto:

     On August 13, 1999, Senator Conrad Burns, Chairman of the Senate
Subcommittee on Communications, sent a letter to William E. Kennard, Chairman of
the Federal Communications Commission (the "FCC") indicating his hope that that
the FCC would act in a timely manner on Parent's application to acquire 49
percent of the Company through classification as an authorized common carrier.

     Senator Burns and Representative Tom Bliley, Chairman of the House
Committee on Commerce, had previously requested in a letter to Mr. Kennard on
January 21, 1999 that the FCC withhold action on Parent's application prior to
Congress adopting satellite reform legislation.  Copies of the January 21, 1999
letter and a related news release issued by Representative Bliley and Senator
Burns were filed as Exhibit (a)(13) to Amendment No. 5 to the Schedule 14D-1
filed with the Commission on January 22, 1999.  A copy of a joint press release
issued by Parent and Company regarding the January 21, 1999 letter was filed as
Exhibit (a)(14) to Amendment No. 5 to the Schedule 14D-1.

     An industry publication has reported that a draft order concerning the
applications of the Purchaser and Parent filed with the FCC (a) to effect a
transfer of control of CGSI and become a common carrier and (b) to acquire 49
percent of the Company through classification as an authorized common carrier
were put on circulation at the FCC late Tuesday, August 17, 1999.  Under typical
FCC procedures, commissioners vote on orders put on circulation within 30 days,
although there is no legal requirement that the commissioners do so.  In
addition, a meeting of the commissioners of the FCC is scheduled for September
15, 1999.  It is possible that the applications may be scheduled for
consideration at the September 15 meeting.  If the FCC acts in accordance with
its past practices, the agenda for that meeting would typically be released by
September 8, 1999.  Neither the Purchaser nor

                              (Page 3 of 8 pages)


Parent knows whether the application will be scheduled to be considered at the
September 15 meeting or whether the commissioners will vote on the circulated
order in accordance with the FCC's 30 day procedure, although, either course
would allow the FCC to act upon the applications prior to September 18, 1999.
The Purchaser and Parent have each stressed to the FCC the importance of action
prior to this date, however, there can be no assurance that the FCC will act
before September 18, 1999 or that any action will be favorable.

     Item 10(f) is hereby amended and supplemented by the addition of the
following paragraphs thereto:

     On August 27, 1999, Parent issued the press release attached hereto as
Exhibit (a)(19) pursuant to which it announced that the Purchaser had extended
the Offer until 12:00 noon, New York City time on Saturday, September 18, 1999.
The terms of the extended Offer otherwise remain the same as those of the
original Offer as set forth in the Offer to Purchase filed with the Securities
and Exchange Commission on September 25, 1998.  The Offer is being extended
because certain required regulatory approvals have not yet been obtained.

     According to First Chicago Trust Company of New York, the depositary for
the Offer, as of the close of business on August 26, 1999, 10,820,526 shares of
Company Common Stock had been validly tendered and not withdrawn pursuant to the
Offer.  None of these shares were tendered pursuant to notices of guaranteed
delivery.

                              (Page 4 of 8 pages)


ITEM 11.    MATERIAL TO BE FILED AS EXHIBITS.

     Item 11 is hereby amended and supplemented by the addition of the following
thereto:

     (a)(19) Text of Press Release issued August 27, 1999.




                              (Page 5 of 8 pages)


                                   SIGNATURE



     After due inquiry and to the best of my knowledge and belief, I certify
that the information set forth in this statement is true, complete and correct.



                                    August 27, 1999



                                    REGULUS, LLC



                                    By:  /s/ Stephen M. Piper
                                        ------------------------------------
                                    Name: Stephen M. Piper
                                    Title: Vice President

                              (Page 6 of 8 pages)


                                   SIGNATURE



     After due inquiry and to the best of my knowledge and belief, I certify
that the information set forth in this statement is true, complete and correct.



                                    August 27, 1999



                                    LOCKHEED MARTIN CORPORATION



                                    By:  /s/  Stephen M. Piper
                                       -----------------------------------
                                    Name:  Stephen M. Piper
                                    Title:   Assistant Secretary

                              (Page 7 of 8 pages)


                               14D-EXHIBIT INDEX

EXHIBIT  DESCRIPTION
- -------  -----------

(a)(19)  Text of Press Release issued August 27, 1999

                              (Page 8 of 8 pages)


                                                                 Exhibit (a)(19)

                                                           For Immediate Release
                                                           ---------------------


TENDER OFFER FOR COMSAT
EXTENDED BY LOCKHEED MARTIN


BETHESDA, Maryland, August 27, 1999 -- Lockheed Martin Corporation (NYSE: LMT)
said today that its wholly owned subsidiary, Regulus, LLC, is extending its
offer to purchase up to 49 percent (less certain adjustments) of the outstanding
shares of common stock of COMSAT Corporation (NYSE: CQ) at a price of $45.50 per
share, net to the seller in cash, until 12:00 noon, New York City time, on
Saturday, September 18, 1999.  The offer is being extended because certain
required regulatory approvals have not yet been obtained.

The offer previously had been scheduled to expire on August 31, 1999. The terms
of the extended tender offer otherwise remain the same as those of the original
offer as set forth in the offering materials filed with the Securities &
Exchange Commission on September 25, 1998.

The proposed Lockheed Martin/COMSAT strategic combination was announced
September 20, 1998.  On August 20, 1999, COMSAT shareholders approved the
proposed merger. Upon completing the transaction, COMSAT will become an integral
element of Lockheed Martin Global Telecommunications, a wholly owned subsidiary
formed by Lockheed Martin to provide terrestrial and satellite networks for
corporate and government customers worldwide.

According to First Chicago Trust of New York, the depositary for the tender
offer, as of the close of business on August 26, 1999, 10,820,526 shares of
COMSAT Corporation had been validly tendered and not withdrawn pursuant to the
offer.  None of these shares were tendered pursuant to notices of guaranteed
delivery.

                                     -more-


The Information Agent for the offer is Morrow & Co., Inc., and questions about
the tender offer may be address to Morrow at 1/800-566-9061.  The Dealer Manager
is Bear, Stearns & Co., Inc., and questions may be address to it at 1/800-762-
5237.

                                     # # #

CONTACT:  Charles Manor, Lockheed Martin Global Telecommunications, 301/581-2720

NOTE:  Statements that are not historical facts are forward-looking statements
made pursuant to the safe harbor provision of the Private Securities Litigation
Reform Act of 1995.  Such forward-looking statements involve risks and
uncertainties that could cause actual results to differ materially from
anticipated results, including the effects of government budgets and
requirements; economic conditions; competitive environment; timing of awards and
contracts; the outcome of contingencies, including litigation and environmental
remediation; and program performance, in addition to other factors not listed.
See in this regard, the Corporation's filings with the SEC.  The Corporation
does not undertake any obligation to publicly release any revisions to forward-
looking statements to reflect events or circumstances or changes in expectations
after the date of this news release or the occurrence of anticipated events.